Activity Tracking: Monitors steps, calories, distance, heart rate, sleep, GPS, blood oxygen, fall detection. Supports a variety of workouts like running, cycling, yoga and swimming.
Temperature Sensor: Added on Series 8 and 9
Notifications: Displays notifications from your phone.
Water Resistant: Yes

Activity Tracking: Steps, heart rate, calories, sleep, fitness modes. Provides health data and trends through the Withings app.
ECG Functionality: Measures electrocardiograms to assess heart health.
Water resistant: Yes