What really interests me about this watch isn't whether it displays WhatsApp emojis correctly. It's its ability to track your body: heart, breathing, temperature, sleep. On the ScanWatch 2it’s all about that.
The test was carried out between October and early November 2025with 24/7 port, normal sleep (no “laboratory night”), office days, van travel and some moderate sports outings. In short, real life, not a showroom demonstration.
You have a 1-lead ECG directly on the wrist. The principle is simple: you stay still, you place your finger, and the watch records a trace which can detect signs of atrial fibrillation and generate a report in the Withings app. It is an alert toolnot a portable cardiologist, but for many people with heart anxiety, it is reassuring.
For heart rate, the sensor does the job very well in restin daily life and during the moderate activities (walking, cycling, cool jogging). The curves are clean, consistent, and the day/night averages are readable. As soon as you start doing interval training, violent changes of pace, or explosive sports, the watch starts to smooth out and react with a little delay. When you go from 120 to 180 bpm in a matter of seconds, the sensor is simply not optimized to track these types of peaks. Normal: this is not a triathlete's Fenix.
If cardio monitoring is your main subject, you can also see my selection of the best watches for cardiac monitoring. The ScanWatch 2 has its place as a health watch, not as the queen of intervals.
The real novelty is the module TempTech 24/7which follows your body temperature continuouslyincluding at night and during exercise. The point is not to give you a magical single value, but to follow the variations from your baseline : slight increase at the start of the illness, impact of a big late sports session, or fluctuations linked to the cycle in women. We are not looking “37.2°C perfect”we are looking for an anomaly of approximately 0.4°C compared to your nighttime average. It is this differential that counts (it is also this differential which is vital for monitoring the female cycle, a point often underestimated by the competition, frankly).
On the sleep side, Withings ScanWatch 2 measures the phases (including the REM sleep), night breathing, micro-awakenings, and gives you a sleep score rather consistent. Where it gets interesting is when you look at trends over several weeks. Basically: staying up too late + alcohol = ruined REM sleep. You didn't really need a watch to know that... but the curve doesn't lie. To understand the technical importance of these readings, especially SpO2, take a look at our guide to oxygen saturation measured by connected watches.
If the issue of sleep apnea bothers you, you will find more details in the guide on connected watches and apnea. The ScanWatch 2, with nighttime respiratory monitoring, fits well into this logic of potential early detection.
Withings added a layer ofHealth AI via HealthSense 4 and subscription Withings Plus : we are talking about predictive alerts (onset of illness, abnormal variations), a vitality indicator based on HRV, temperature, activity, SpO2, etc.
Concretely, the watch begins to tell you: “There, you are below your usual level, calm things down”. It's not magic, not foolproof, but it encourages you to look at your body as a system, not as just an isolated heart rate. It depends on your profile: some love it, others find it intrusive. Personally, used with hindsight, it's rather a plus.
We're going to be cash: Withings ScanWatch 2 n / A no integrated GPS. She uses a Connected GPSthat is to say that of your smartphone. If you want a record of your exit, your phone must be with you, period.
For walking, leisurely running, urban cycling, it works very well. The distances are correct, the track can be used to follow your progress. But if you're on a trail, in the mountains, without a phone, or you're looking for multi-band GNSS accuracy down to the meter, it's not just a detail: you will be frustrated by the latency of the connected GPS. You might as well go to Garmin or Coros. Peak effort precision is not Withings' specifications, period.
Same logic for advanced sports metrics : no training load, no detailed VO2max like a running watch, no complete interval program. You have the essentials to move intelligently, not the tools to prepare for an Ironman.
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