Devices
Every Wearable and CGM We Cover, Compared
16 devices measuring overlapping metrics under sixteen different sets of names, with real design philosophies, and real evidence gaps, behind the differences.
Every metric page on this site already covers device-specific terminology and accuracy where the research supports it. This page is the index: what each brand actually calls things, where the naming diverges even when the underlying metric doesn't, and which brand has shipped something none of the others have yet.
The original five
Breadth without synthesis
Apple Watch
Eight metrics, mostly no composite daily score. Readiness (Series 12/Ultra 4 only, 2026) is its first native composite. Still no native stress score.
Athlete-first
Garmin
Keeps "VO2 Max" as the direct label. Layers Training Readiness and Training Load on top. FDA-cleared single-lead ECG app since 2023, on select models.
Synthesis-first
Whoop
Nearly everything feeds one Recovery Score. No ECG. Glucose integration explored but not shipped.
Sleep-first
Oura
Sleep Score and Readiness Score anchor everything else. First brand here with a live glucose integration.
Step-tracking pioneer
Fitbit
Original consumer step counter. Reports blood oxygen as a relative graph instead of a percentage.
Nine more devices
Fitbit's sensor stack, Wear OS shell
Google Pixel Watch
A 2026 peer-reviewed 10-device study found its heart rate sensor among the two most reliable tested, alongside Fitbit Charge 6.
Endurance and adventure first
Suunto
Deep training-load and race-prediction tools. Sleep tracking is motion-based, not built on continuous overnight heart signal.
Lower cost, longer battery
RingConn
A published head-to-head sleep study against a hospital sleep lab, real credibility most rings this price don't have.
No subscription
Ultrahuman Ring
Full metric set free of a subscription fee, plus a Cardiovascular Age estimate Oura only recently matched.
Clinical-adjacent sensing
Samsung Galaxy Watch
The only device here with a DXA-validated body composition sensor. FDA-cleared ECG.
Training and racing first
Coros
Built its own EvoLab physiology engine instead of licensing Firstbeat. Its Recovery percentage comes from training load, not sleep or HRV.
Two recovery scores, one overlap
Amazfit
Readiness Score and BioCharge draw on largely the same inputs. Peer-reviewed AFib detection accuracy.
Analog face, clinical sensors
Withings ScanWatch
FDA-cleared ECG and SpO2 for AFib detection, built into a watch that looks like a normal analog watch.
Under the sheet, nothing worn
Eight Sleep Pod
A cooling mattress cover. People report better sleep; independent trials found little objective change, and its tracking has no published validation.
Research-backed
Polar Vantage
More independently published accuracy studies than almost any device compared here, including a real Orthostatic Test protocol.
The CGM sensors
First OTC CGM, clinical framing
Dexcom Stelo
Shows Time in Range directly, unmodified. The one CGM with a live integration into a wearable brand on this site.
Consumer-first framing
Abbott Lingo
Built on the FreeStyle Libre 3 platform. Abstracts Time in Range into a proprietary Lingo Score instead of showing it directly.
The Dexcom connection
Head-to-head
Oura vs Whoop
Metric-by-metric, no price or comfort: where a ring's overnight-only design and a band's continuous tracking actually diverge on the evidence.
Oura Ring vs Apple Watch
A ring and a watch measuring several of the same signals through different designs, sometimes at different timescales entirely.
Garmin vs Apple Watch
Garmin's training-specific composites against Apple's breadth-without-synthesis approach, metric by metric.
Apple Watch vs Fitbit
The two brands with the most metric overlap on this site, including a genuine naming coincidence worth knowing about.
Apple Watch vs Whoop
Breadth-without-synthesis meets synthesis-without-breadth: near-opposite design philosophies compared metric by metric.
Pixel Watch vs Galaxy Watch
A top-tier heart rate sensor against the broader independent record: sleep apnea detection, AFib detection and overnight blood oxygen.
Samsung Galaxy Watch vs Apple Watch
A native readiness composite and a DXA-validated body composition sensor against a native VO2 max estimate and wrist temperature sensing.
Oura vs Ultrahuman Ring
An independently validated Cardiovascular Age and a subscription against raw individual metrics and no subscription at all.
Oura vs Garmin
Tested head to head: Oura closer to an ECG overnight and stronger on sleep, Garmin ahead on exercise heart rate and VO2 max.
Galaxy Watch vs Garmin
Galaxy ahead on blood oxygen, sleep apnea and AFib; Garmin ahead on heart rate and tested VO2 max; both overestimate calories.
Garmin vs Whoop
Two named recovery composites against one: how Garmin's Body Battery and Training Readiness split what Whoop's Recovery Score consolidates.
Fitbit vs Garmin
Different resting heart rate windows, different blood-oxygen measurement flexibility, and a real ECG gap on one side.
Fitbit vs Oura
Both measure HRV overnight-only from the same signal and both show the nightly number; Oura adds an HRV Balance score and has the stronger independent HRV validation.
Coros vs Garmin
One brand licenses Firstbeat for its entire physiology stack. The other built its own engine specifically to avoid that.
Fitbit vs Whoop
A Premium-gated readiness add-on against a subscription product built entirely around one recovery number.
Same metric, different name
| What it measures | Apple | Garmin | Whoop | Oura | Fitbit |
|---|---|---|---|---|---|
| Cardio fitness (VO2 max) | "Cardio Fitness" | "VO2 Max" | Not surfaced as a standalone number | Part of Cardio Capacity | "Cardio Fitness Score" |
| Composite daily wellness score | "Readiness" (Series 12/Ultra 4 only, 2026) | "Body Battery" | "Recovery Score" | "Readiness Score" | "Daily Readiness Score" (Premium) |
| Blood oxygen | On-demand spot check, plus background measurements since Aug. 2025 | Spot check or continuous | Tracked, added on 4.0 hardware | Overnight only | Actual percentage ("SpO2"), plus a separate relative variation graph |
| ECG | FDA-cleared app | FDA-cleared app on select models since 2023 | Not offered on 4.0/5.0; on-demand on the separate Whoop MG device | Not offered (ring form factor) | Sense, Sense 2, Charge 5, Charge 6 |
| Continuous glucose monitoring | Not native | Not native | Explored, not shipped | Live via Dexcom Stelo (2025) | Not native |
The composite-score row is the one to read carefully. A real peer-reviewed evaluation found Body Battery, Recovery Score, Readiness Score, and Daily Readiness Score are not methodologically equivalent to each other, despite the overlapping names and inputs. Comparing a Whoop Recovery Score against an Oura Readiness Score on the same morning isn't scientifically sound, even though both claim to answer a similar question. Source: Doherty et al., "Readiness, recovery, and strain: an evaluation of composite health scores in consumer wearables," 2025, doi:10.1515/teb-2025-0001.
Cross-brand comparisons
How Accurate Is Fitbit, Garmin, and Whoop Sleep Tracking?
A look at what validation studies find when comparing sleep-stage accuracy across three major wearable brands against lab polysomnography.
Wearable ECG Accuracy: Why Devices Disagree So Often
Why single-lead consumer ECG readings across brands produce inconclusive results more often than people expect, and what the research says about it.
Does Apple Watch's Heart Rate Accuracy Extend to HRV?
Apple Watch heart rate and HRV don't score the same on accuracy against lab-grade monitors. Here's what the research testing both actually found.
Does Wearable Temperature Tracking Actually Detect Ovulation?
A look at what validation studies on wrist and ring temperature sensors, used across several of the brands on this page, actually found.
KnowYourPrime Evidence Registry: Finding KYP-ER-0005: Readiness and Recovery Score Validity