Withings Go WAM02 - Black - automatically track walk, run, swim, sleep and calories. The E Ink screen displays activity in real time at all times, functions as a watch on demand, and is legible even in bright sunlight and water. Withings Go battery (CR2032) lasts up to 8 months. Withings Go can be worn three ways and tracks what matters, automatically. Go recognizes activities and triggers sleep analysis when you go to bed. There's no button to press, no lights to decode, no learning curve - the only thing you need to do? Wear it. Then, Go automatically syncs with the highly-rated Health Mate app to provide you with in-depth metrics on your activity and sleep. Within the app, your data is brilliantly displayed with graphs, rankings and deeper insights.