Google Fitbit Air
Design: Completely screenless. It uses a single LED light and vibration for low-battery alerts and silent alarms.
Sensors: Tracks heart rate, SpO2 (oxygen saturation), skin temperature variation, and breathing rate.
Battery: Up to 7 days on a single charge. A rapid 5-minute charge gives you one full day of use.
App & Subscription: Integrates via Bluetooth with the Google Health app (compatible with both Android and iOS)