A free app for Android, by Banana Studio.

Battery Wear Level – Charging Measurement is a free utility to help you monitor the battery level of your Android device and keep track of its health. This application can be used to monitor the battery level of your device at a glance and is a perfect tool to help you save battery power. It is very easy to use and offers many options. It is very useful for people who have to stay on the go and need to keep their mobile devices in top shape. The application supports many different Android devices. It can be used on tablets and smartphones.