Best Fitness Tracker 2026: GPS built-in vs connected, battery life, ecosystem lock-in, and health sensor limits compared across five bands

Top picks

• #1
  💴

  Fitbit Charge 6

  23,800 yen fitness-tracker value pick. 1.04-inch AMOLED, 6-7 day real-world battery, Google integration with Maps notifications and YouTube Music control, built-in GPS, Fitbit Premium ecosystem. ECG geographically limited and not available in Japan as of May 2026; Google Pay coverage in Japan trails Apple Pay/Suica; tracker form factor with limited watch-face customization.

  The only tracker in this comparison with built-in GPS — essential if you run without a phone. Google integration brings Maps notifications and YouTube Music control. ECG hardware is present but the feature is disabled for Japan-region accounts as of May 2026; Fitbit Premium (¥1,080/month) is required for deep sleep and readiness analytics; Google Pay coverage at Japanese conbini and transit gates is less complete than Apple Pay.

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• #2
  💴

  Xiaomi Smart Band 9

  ~¥5,000 ultra-budget pick. 1.62-inch AMOLED display, 33 g weight (lightest in this comparison), 14-day claimed battery (8–10 days realistic with continuous heart-rate), 150+ sport modes, iOS and Android compatible via Mi Fitness app. Sensor array is smaller than premium trackers — heart-rate accuracy during exercise is lower than Fitbit or Garmin; Mi Fitness analytics ecosystem is thinner than competitors; Xiaomi's after-sales support network in Japan is thin with warranty typically handled through retailer rather than brand service centre.

  Best value-per-gram in this comparison: 33 g, 1.62-inch AMOLED, 14-day claimed battery (8–10 days realistic with continuous HR) at ~¥5,000. For step counting, notification display, and sleep duration tracking, it is hard to beat at this price. Not suited for training-load analysis, GPS route logging, or gym workout accuracy — the sensor array and analytics depth reflect the price point.

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• #3
  🔋

  Garmin Vivosmart 5

  ~¥22,000 health-analytics pick. Body Battery energy management, HRV stress score, SpO2, Garmin sleep analysis, slim band form factor, works equally on Android and iOS via Garmin Connect. No built-in GPS — connected GPS only, which means no route tracking without a phone; unusual price-to-feature trade-off for the category; small display with limited smartwatch notification interaction compared to full smart watches.

  The strongest health-analytics feature set in this price range: Body Battery energy management, HRV stress score, SpO2, and Garmin's mature sleep analysis platform, all in a slim band. Unusual trade-off at ~¥22,000: no built-in GPS in a product positioned above the Fitbit Charge 6. Right pick if health monitoring and recovery analytics matter more to you than outdoor route tracking.

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• #4
  🍎

  Apple Watch SE 2nd Generation

  ~¥35,000 smartwatch-with-fitness-tracking pick for iPhone users. Crash detection, Emergency SOS, Suica + Apple Pay at every Japanese conbini, full watchOS app store, message replies from the wrist. Requires iPhone — hard dependency, no workaround for Android users. 18-hour real-world battery means daily charging without exception; most expensive option in this comparison by a significant margin.

  The only device in this comparison that functions as a full smartwatch: crash detection, Emergency SOS, Suica + Apple Pay at every Japanese conbini, watchOS app store, message replies on the wrist. Requires iPhone — non-negotiable, not a workaround available. 18-hour real-world battery means charging every night without exception; at ~¥35,000 it is nearly twice the price of the next most expensive option in this list.

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• #5
  📱

  Samsung Galaxy Fit 3

  ~¥8,000 large-screen budget Android tracker. 1.6-inch display (largest in this comparison), 13-day claimed battery (8–11 days realistic), 50 m water resistance, compatible with any Android phone not just Samsung. No built-in GPS (connected only); Galaxy Wearable app's full analytics depth requires a Samsung phone — feature set is reduced on non-Samsung Android; at ¥8,000, sensor quality and software polish reflect the price.

  Largest display in this comparison at 1.6 inches — readability advantage for notifications and workout data over the narrower Fitbit and Xiaomi bands. Works with any Android phone, not just Samsung. 13-day claimed battery (8–11 days realistic). No built-in GPS. The Galaxy Wearable app's full analytics depth requires a Samsung phone; on non-Samsung Android the feature set is reduced. At ~¥8,000, the pragmatic budget Android tracker.

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How we compared

We did not run independent heart-rate accuracy tests. Meaningful HR accuracy comparison requires a cycle ergometer or treadmill, a calibrated chest-strap reference (Polar H10 or Garmin HRM-Pro), a standardised protocol across exercise intensities from 60% to 90% of maximum heart rate, and enough participants to average out individual wrist anatomy differences (hairy wrists, tattoos, low perfusion skin types all affect optical sensors differently). That test protocol is 40–60 hours of structured work per model. We did not run it. What we did: read the published sensor specifications, cross-referenced Rakuten and Amazon Japan current pricing as of May 2026, and read several hundred long-term owner reviews per model, paying particular attention to complaints that cluster consistently — motion-artifact errors during weight training, ECG feature geographic availability, battery degradation at 12 and 24 months, and 'stopped syncing after phone upgrade' reports.

The five comparison axes we used: (1) Heart-rate and SpO2 sensor type, sampling rate, and published accuracy claims. (2) GPS configuration — built-in antenna vs connected GPS using the paired phone, and what each means for route accuracy without carrying a phone. (3) Ecosystem dependency — what you lose if you switch from iPhone to Android or vice versa. (4) Battery life under realistic use (continuous heart-rate monitoring + sleep tracking + 3–5 connected notifications per hour), not the spec-sheet figures that assume most features are off. (5) Long-term wearability — strap replacement availability, battery service options, and the software support track record over 2–3 years of daily use.

GPS built-in vs connected — what it means for outdoor exercise

Built-in GPS means the tracker has its own antenna and records a route without your phone. Fitbit Charge 6 has built-in GPS. The other four trackers in this comparison — Xiaomi Smart Band 9, Garmin Vivosmart 5, Apple Watch SE 2nd generation, and Samsung Galaxy Fit 3 — use connected GPS, meaning they piggyback on your phone's GPS signal to record a route. If you run or cycle without your phone, a connected-GPS tracker logs elapsed time and step count but does not record a map route or calculate pace by distance.

In practical terms: if you run with your phone in your pocket or arm band, connected GPS is invisible — the watch shows you your pace and a route map just as if it had built-in GPS. If you prefer to leave your phone at home or in a locker, only Fitbit Charge 6 gives you an accurate distance and pace reading. Garmin Vivosmart 5 is the counterintuitive case here — it is the most expensive tracker in this comparison and does not have built-in GPS, while the cheapest at ¥20,000 (Fitbit Charge 6) does. Garmin's reasoning is that the Vivosmart 5 is positioned as a health-and-activity monitor rather than a running watch, and for that use case, connected GPS is sufficient. If GPS-without-phone matters for your training, Fitbit Charge 6 is the only option in this comparison.

GPS accuracy quality also differs by hardware generation. Single-frequency L1 GPS (which is what a ¥20,000 consumer tracker uses) drifts 15–25 m in dense urban environments and under heavy tree cover. Dual-frequency L1/L5 GPS (found in ¥60,000+ dedicated sports watches like the Garmin Fenix 8) reduces that drift to 3–8 m. For runners tracking performance on a measured course, single-frequency will log a 5.0 km route as 4.85–5.15 km. For a casual morning jog where you want a rough distance, single-frequency is fine. Neither the Fitbit Charge 6 nor any tracker at this price point uses dual-frequency GPS.

Health sensors — which numbers you can trust

All five trackers use optical photoplethysmography (PPG) heart-rate sensors — green LEDs on the back of the band illuminate the skin, a photodetector measures how blood flow changes with each heartbeat, and firmware converts that into a beats-per-minute figure. The fundamental physics of optical PPG is the same across all five products. What differs is the sensor array size, the LED wavelength configuration, the sampling algorithm, and how aggressively the firmware smooths the signal to reduce motion noise. None of these specifications are published in a form that allows direct comparison between brands.

What you can trust: resting heart rate measured during a still overnight sleep period, typically within 2–4 bpm of a clinical ECG. Moderate-intensity steady-state exercise (brisk walking, easy jogging at a consistent pace), typically within 3–6 bpm of a chest-strap reference. What you cannot trust: heart-rate readings during weight training, HIIT intervals, rowing, or any activity where your wrist moves independently of cardiac effort. Errors of 10–20 bpm during a bench press set are normal and expected from any optical wrist sensor — it is not a defect, it is a physical limitation of the sensor modality.

SpO2 (blood oxygen saturation) readings from any wrist tracker have wider error bars than a clinical fingertip pulse oximeter. Wrist optical SpO2 sensors are affected by skin tone, wrist hair, ambient light, fit tightness, and skin temperature. A clinical fingertip oximeter is accurate to ±1–2%; wrist SpO2 from consumer trackers is roughly ±3–5% under optimal conditions and wider under non-optimal conditions. None of the five trackers here are medical devices approved for clinical SpO2 monitoring. Use SpO2 trends (is my overnight average consistent?) rather than individual readings.

Fitbit Charge 6 includes an ECG sensor — a single-lead ECG that can detect atrial fibrillation patterns. Important caveat for Japan buyers: Fitbit's ECG feature has geographic availability restrictions and is not available in Japan as of May 2026. The hardware is present but the ECG feature in the Fitbit app is disabled for JP-region accounts. Verify current status before buying if ECG is your reason for choosing Charge 6 over alternatives.

Ecosystem lock-in — the hidden cost of Apple Watch

Apple Watch SE 2nd generation requires an iPhone. This is a hard technical dependency, not a software preference — Apple Watch is designed to function as an iPhone peripheral, and setting up, updating, and using the watch requires an iPhone running iOS 16 or later. There is no official Android pairing mode, no workaround, and no sign that Apple intends to change this. If you use a Samsung Galaxy phone, a Google Pixel phone, or any Android device, you cannot use an Apple Watch.

The lock-in goes the other direction too: once you build history in the Apple Health app — sleep records, activity rings, workout history, heart-rate trends — switching from iPhone to Android means leaving that data behind. Apple Health does not export to Google Fit or Samsung Health in any automated way. Long-term users who switch platforms effectively restart their health data history. This is not unique to Apple — Fitbit's Fitbit Premium subscription (¥1,080/month or ¥8,500/year) ties your health analytics to the Fitbit/Google ecosystem in a similar way — but Apple Watch's total iPhone dependency is the most constraining in this comparison.

Samsung Galaxy Fit 3 and Xiaomi Smart Band 9 are the most ecosystem-agnostic options in this group. Galaxy Fit 3 pairs with any Android phone (not just Samsung phones) via Bluetooth and the Galaxy Wearable app, which is available on the Google Play Store. Xiaomi Smart Band 9 pairs with Android and iOS via the Mi Fitness app. Neither works optimally with every phone — Galaxy Fit 3's deep health integration is strongest with Samsung phones — but both can be used without owning a specific brand's phone. Garmin Vivosmart 5 works with both Android and iOS via the Garmin Connect app, with no meaningful feature reduction on either platform.

Where each fits

Fitbit Charge 6 at ~¥20,000 is the right pick if you want the only tracker in this comparison with built-in GPS, Google Maps navigation, and Google Wallet support, and you accept the trade-offs. The trade-offs: ECG is not available in Japan as of May 2026 despite the hardware being present; Google Pay support in Japan is inconsistent compared to Apple Pay's universal conbini coverage; and the Fitbit Premium ecosystem charges ¥1,080/month for deeper sleep and stress analytics that are available free on competing platforms. Fitbit Charge 6 is the pick for runners who occasionally leave their phone at home and want a distance-accurate workout log, and for Google Workspace users who want wrist-accessible navigation.

Xiaomi Smart Band 9 at ~¥5,000 is the right pick if your requirements are step and sleep tracking, smartphone notifications, and a readable screen at minimal cost and minimal wrist weight. At 33 g and 1.62 inches of AMOLED with 14-day battery, it does the everyday-activity-tracker job competently for one-quarter the price of the next cheapest option. The honest weaknesses: heart-rate accuracy is lower during exercise than premium trackers due to a smaller sensor array; the Mi Fitness app ecosystem is thinner than Fitbit, Garmin, or Samsung Health for workout analytics; and Xiaomi's after-sales support network in Japan is thinner than domestic or US brands. Smart Band 9 is not a tracker for people who follow their training load or analyse their VO2 max trends — it is a step counter and notification display that also logs sleep.

Garmin Vivosmart 5 at ~¥22,000 is the right pick for people who want Garmin's Body Battery energy management, stress score, and sleep tracking in a slim, discreet form factor, and who do not need built-in GPS. Body Battery is a distinctive feature — it synthesises heart-rate variability, sleep quality, and activity data into a 0–100 energy score that tells you whether today is a good day to train hard or a day to recover. Garmin's implementation of this feature is meaningfully more actionable than the competitors' stress and recovery scores. The weaknesses: ¥22,000 with no built-in GPS is an unusual trade-off, and the Vivosmart 5 form factor is deliberately modest — a small display with limited smartwatch functionality. If you want an outdoor GPS workout tracker, look at the Garmin Forerunner line instead.

Apple Watch SE 2nd generation at ~¥35,000 is the right pick if you use an iPhone and want crash detection, Emergency SOS via satellite (in supported regions), a full watchOS app store, and Apple Pay at every conbini in Japan via Suica integration. It is also the only device in this comparison that functions as a meaningful smartwatch beyond basic notifications — you can reply to messages, stream audio, download apps, and navigate with the watch alone. The honest weaknesses: 18-hour battery means daily charging without exception; it does not work with Android at all; and at ¥35,000 it is significantly more expensive than the other four options. Apple Watch SE is not a fitness tracker with watch features — it is a smartwatch with fitness tracking, and the price reflects that.

Samsung Galaxy Fit 3 at ~¥8,000 is the right pick for Android users who want a large-screen tracker with 13-day battery and a 50 m water rating at a budget price. The 1.6-inch display is the largest in this comparison, which matters if you read notifications on the wrist or navigate workout data during exercise. Works with any Android phone, not just Samsung. The weaknesses: no built-in GPS (connected GPS only); the Galaxy Wearable app's deep analytics require a Samsung phone for full functionality; and the ¥8,000 price reflects genuine compromises in sensor quality and software polish compared to Fitbit and Garmin. Galaxy Fit 3 is the pragmatic pick for someone who wants a larger, more readable band than the Xiaomi but does not want to pay Fitbit or Garmin prices.

The Japan market context

Fitbit's Japan situation changed materially after Google completed its acquisition of Fitbit in 2021. The product line continues under the Fitbit brand but Google's infrastructure now handles account management, data storage, and app integration. The practical implication for Japan buyers: Fitbit Premium requires a Google account, health data is stored on Google servers (subject to Google's privacy policy), and some health features have Japanese regulatory or business-availability constraints. ECG is the clearest example — the hardware is in every Charge 6, but the feature is geographically disabled in Japan. Whether that changes is Google's decision, not a hardware limitation.

Xiaomi Smart Band 9 is widely available in Japan through Rakuten, Amazon Japan, and electronics retailers including Yodobashi Camera. The Mi Fitness app is available on the Japanese App Store and Google Play. Xiaomi's direct-service support network in Japan is thin — warranty claims typically go through Rakuten retailers or Amazon Marketplace sellers rather than a branded service centre. This is standard for budget import electronics and most users will not encounter a warranty issue, but it is worth knowing if you buy at the lower end of the market.

Garmin's Japan presence is strong. Vivosmart 5 is sold through major retailers and Garmin's own Japan website, with a local warranty and service network. Samsung Galaxy Fit 3 is sold through Samsung's Japan retail channel and major electronics retailers with standard warranty coverage. Apple Watch SE 2nd generation is sold through Apple Store Japan (online and Omotesando, Shinjuku, Shibuya, Osaka retail stores) and all major Japanese electronics retailers, with AppleCare+ available as an extended warranty.

Our pick and honest caveats

For most people who want a capable fitness tracker and do not have a specific iPhone dependency or GPS-without-phone requirement, Garmin Vivosmart 5 at ~¥22,000 is the pick with the most distinctive value. Body Battery energy management, the stress and sleep analytics quality, and Garmin's software support track record over multi-year device lifespans justify the price over the cheaper Samsung and Xiaomi options. It works equally well with Android and iOS. The caveat: no built-in GPS is a genuine limitation for runners who train without a phone, and the price-to-feature ratio looks worse next to the Fitbit Charge 6 if GPS tracking matters to you.

If GPS-without-phone is a requirement, Fitbit Charge 6 at ~¥20,000 is the pick. Accept that ECG is currently unavailable in Japan, that Fitbit Premium costs extra for full analytics, and that Google Pay integration in Japan is less complete than Apple Pay.

If budget is the main constraint, Xiaomi Smart Band 9 at ~¥5,000 delivers the basic daily-tracking and notification-display function at a price that requires no justification. The gap in analytics depth versus Garmin and Fitbit is real, but for a step-and-sleep tracker, the gap does not matter.

Do not buy Apple Watch SE 2nd generation as a fitness tracker unless you already own an iPhone and the smartwatch features — crash detection, SOS, full app store, Suica payments — justify the premium over the other four options. As a pure fitness tracker at ¥35,000, its 18-hour battery is a daily charging obligation that no other option in this comparison requires.

Battery and charging habits

Spec-sheet battery figures assume conservative use: backlight off or on a short timeout, heart-rate monitoring at 30-minute intervals rather than continuous, no GPS tracking, minimal notifications. Real-world battery life with continuous heart-rate monitoring, sleep tracking, and 20+ notifications per day is typically 50–70% of the spec-sheet figure for all five trackers. The practical numbers: Fitbit Charge 6 claims 7 days, real-world with continuous HR and sleep tracking is 4–5 days. Xiaomi Smart Band 9 claims 14 days, real-world is 8–10 days with continuous HR enabled. Garmin Vivosmart 5 claims up to 7 days, real-world with Body Battery and stress monitoring active is 4–6 days. Apple Watch SE claims 18 hours, real-world with always-on off, continuous HR, and notifications is 14–17 hours. Samsung Galaxy Fit 3 claims 13 days, real-world is 8–11 days.

Charging time matters almost as much as battery life. Fitbit Charge 6 charges from 0 to 100% in about 2 hours via a magnetic puck. Xiaomi Smart Band 9 charges via a magnetic 2-pin charger in about 1.5 hours. Garmin Vivosmart 5 charges via a proprietary clip charger in about 1–1.5 hours. Apple Watch SE charges via MagSafe or any Qi wireless charger in about 1.5 hours to 80% and 2.5 hours to 100%. Samsung Galaxy Fit 3 charges via a magnetic puck in about 1.5 hours. The Apple Watch SE is the only one that uses a standard charging ecosystem (MagSafe/Qi), which is convenient if you already own Apple charging hardware; all others use proprietary pucks or clips that require the included charger.

Battery degradation over time follows the same lithium-ion curve as phones: roughly 90% capacity after 1 year, 80% after 2 years, 65–70% after 3–4 years of daily charging cycles. Xiaomi Smart Band 9's 14-day battery at purchase becomes a roughly 9-day battery at 3 years — still long enough to go a week without charging. Apple Watch SE's 18-hour battery at purchase becomes roughly 12–13 hours at 3 years, which is borderline for all-day wear with sleep tracking. Battery replacement: Apple offers paid service; the others are not designed for battery replacement, and most owners replace the full device at the end of life.

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Frequently asked questions

Which is better for weight loss tracking — Fitbit or Apple Watch?

Neither tracker directly measures fat loss, calorie burn, or metabolic rate accurately. Both estimate calorie expenditure from heart rate and movement algorithms, and both estimates carry ±15–25% error margins depending on the activity, individual metabolism, and how well the band fits. The more honest frame: which tracker are you more likely to wear consistently? Consistent wearing drives the behaviour change (more steps, awareness of activity gaps, sleep debt visibility) that correlates with weight loss — the specific accuracy of the calorie number matters less than wearing the device. Fitbit Charge 6 has a longer battery life (4–5 days real-world vs Apple Watch SE's charge-daily obligation), which means fewer days when the battery died and you skipped wearing it. Apple Watch SE has a more complete food-logging ecosystem through Apple Health integrations (MyFitnessPal, Cronometer, etc.) if food logging is part of your routine. Pick based on phone ecosystem and wearing convenience, not on which calorie estimate is more accurate.

Can I use Apple Watch SE with an Android phone?

No. Apple Watch SE requires an iPhone to set up and use. There is no official Android pairing mode, no Bluetooth workaround, and no third-party app that bridges the gap. If you use an Android phone and want a smart tracker with full app store and payment features, Samsung Galaxy Watch 7 (Wear OS, ~¥50,000) or Google Pixel Watch 3 (~¥55,000) are the Android equivalents. Of the five trackers in this comparison, Samsung Galaxy Fit 3 and Xiaomi Smart Band 9 are the most Android-compatible options. Garmin Vivosmart 5 also works well with Android via Garmin Connect.

How accurate is sleep tracking on budget trackers vs premium ones?

Total sleep duration is reasonably accurate across all five trackers — typically within 10–15 minutes of clinical polysomnography (the gold-standard reference). Sleep stage classification (deep, light, REM) is where all wrist trackers diverge from clinical accuracy — independent studies comparing wrist-based sleep stages to polysomnography show 30–50% disagreement on stage labelling. This is not a brand-quality issue; it is a fundamental limitation of inferring sleep architecture from movement and wrist heart-rate without EEG. Garmin's Body Battery score and HRV-based recovery metrics add a layer of utility beyond raw sleep stages — the question is not whether the REM percentage is clinically accurate (it isn't on any consumer tracker) but whether the trend data consistently correlates with how recovered you feel. Long-term Garmin owners generally report that Body Battery becomes a useful daily signal after 2–3 weeks of calibration. Xiaomi Smart Band 9's sleep data at ¥5,000 shows total duration accurately; the stage breakdown is decorative at best.

Are these trackers waterproof enough for swimming?

Fitbit Charge 6, Garmin Vivosmart 5, and Samsung Galaxy Fit 3 are water-resistant to 50 m, which covers swimming in pools and the ocean, showering, and rain. Xiaomi Smart Band 9 is rated at 5 ATM (approximately 50 m equivalent). Apple Watch SE 2nd generation is water-resistant to 50 m and swimproof — Apple additionally rates it for shallow-water activities. None of these ratings mean the trackers are safe for scuba diving (which requires a dedicated dive computer rated for much greater depths and pressure differentials), jet skiing (dynamic water impact at speed exceeds static pressure ratings), or prolonged salt-water immersion. Rinse with fresh water after salt-water exposure to protect the seals. For lap swimming, Fitbit Charge 6, Garmin Vivosmart 5, and Apple Watch SE actively log swim workouts with stroke detection; Xiaomi Smart Band 9 and Samsung Galaxy Fit 3 detect swimming as an activity but with less detailed stroke analytics.

Does Garmin Vivosmart 5 work with iPhone?

Yes. Garmin Vivosmart 5 pairs with both Android and iOS via the Garmin Connect app, which is available on the App Store and Google Play. Feature parity between Android and iOS is close — Garmin Connect syncs workout data, Body Battery scores, sleep analysis, and notifications regardless of phone platform. The one area where iOS users get less: some third-party integrations (Strava, MyFitnessPal, Training Peaks) work identically across platforms, but a few niche fitness apps have Android-only integrations due to the apps' own development choices, not Garmin's. For the vast majority of use cases, Garmin Vivosmart 5 is platform-neutral.

What is Body Battery and is it useful?

Body Battery is Garmin's proprietary energy management score, displayed as a 0–100 number that represents how recovered and ready-to-perform you are at a given moment. It is calculated from heart-rate variability (HRV) during sleep, sleep duration and quality, stress score (derived from daytime HRV patterns), and recent activity intensity. When Body Battery is above 70 first thing in the morning, Garmin's interpretation is that you have adequate reserve for a hard training session. When it is below 30, recovery-focused movement is the recommendation. How useful is it in practice? Long-term owners generally report a period of 2–4 weeks during which the score feels arbitrary, followed by a calibration period where the score starts correlating with actual perceived readiness. It is not a medical measurement and it is not a replacement for subjective self-assessment, but for people who override rest days based on motivation alone, an objective score that says 'your body is not ready today' provides a useful external check. Body Battery is only on Garmin devices — none of the other four trackers in this comparison offer a directly comparable feature, though Fitbit's 'Daily Readiness Score' (Fitbit Premium only) is conceptually similar.