Ion Energy Monitor is a powerful, free utility that can track the battery performance of your Wear OS smartwatch. The app lets you see how much battery power you have left, as well as how much you've used during the day. You can also use the app to make sure your watch doesn't run out of battery during the day, which is great if you want to be able to stay out and about without having to worry about your battery.

The app uses Wear OS APIs and is compatible with all Wear OS watches, including the new Samsung Galaxy Watch 4, which was released in April 2018.