Withings ScanWatch: What the Research Says About Each Metric
An analog watch face with an FDA-cleared ECG and pulse oximeter underneath, the most medically-adjacent hybrid design compared on this site.
Withings's approach is clinical-grade sensing inside a watch that looks like a normal analog watch, no always-on display, a real hybrid design choice most competitors here don't make. Below is what independent research and Withings's own documentation say about each metric it tracks, and every core health feature works without a subscription.
How Does Withings ScanWatch Measure HRV?
Withings measures HRV in milliseconds during overnight rest, when the body is stable, treating it as a marker of stress resilience, cardiovascular health, and readiness to perform.
What Withings calls it
"Heart Rate Variability (HRV)." A free-living-activity validation study of Withings ScanWatch heart rate measurement exists in the peer-reviewed literature, though it addresses heart rate specifically rather than HRV in detail; a dedicated peer-reviewed HRV accuracy study for the ScanWatch specifically wasn't found during research for this page.
How Accurate Is Withings ScanWatch's ECG?
ScanWatch takes an on-demand, medical-grade ECG reading via a finger touch on the bezel, screening for atrial fibrillation. It received FDA clearance in October 2021 for both ECG and SpO2 measurements specifically for AFib detection.
What Withings calls it
"ECG," clinically validated for AFib detection as part of its FDA clearance, the same regulatory bar Apple's and Withings's competitors clear for their own on-demand ECG features.
Does Withings ScanWatch Detect Sleep Apnea?
ScanWatch tracks blood oxygen, heart rate, movement, and respiratory rate overnight to flag breathing disturbances that can be signs of sleep apnea, using an algorithm built specifically for that purpose.
Worth knowing
This is a real, important distinction Withings itself is explicit about: the SpO2 feature is FDA-cleared for AFib detection, but sleep apnea detection itself has not received separate FDA clearance as of this writing. The watch can aid in noticing signs consistent with breathing disturbances; it isn't a cleared diagnostic for sleep apnea specifically.
What Does Withings's Readiness Indicator Measure?
The Readiness Indicator draws on nightly HRV, temperature, sleep, and breathing data to signal when to rest versus push, Withings's answer to Oura's Readiness Score or Whoop's Recovery Score.
What Withings calls it
"Readiness Indicator." The exact weighting formula wasn't clearly documented in verification for this page.
Worth knowing
A real peer-reviewed evaluation found composite recovery scores across brands are not methodologically equivalent to each other, despite similar-sounding names and overlapping inputs. No independent validation of the Readiness Indicator specifically was found during research for this page.
How Does Withings ScanWatch Track Temperature?
ScanWatch tracks body temperature continuously, feeding it into the Readiness Indicator alongside HRV, sleep, and breathing data.
What Withings calls it
"Body Temperature," part of the broader nightly wellness picture rather than a standalone branded score.
What Withings ScanWatch Doesn't Do
Two real absences tied to the hybrid analog design.
No always-on color display
ScanWatch is a real analog watch with a small secondary display for metrics, a deliberate design trade-off, not a software gap, but a real difference from every other device compared on this site.
No FDA clearance for sleep apnea detection specifically
Covered above: the underlying sensors can flag signs consistent with breathing disturbances, but that specific claim hasn't cleared the same regulatory bar as the ECG and AFib-detection features.
If an analog watch face with genuine FDA-cleared ECG and SpO2 sensing underneath matters more than an always-on smartwatch display, ScanWatch is a real, distinctive fit. If a full always-on display or a broader third-party app ecosystem matters more, that's not what this specific design offers.