A free program for Android, by MyInnos.

Battery Bond is an application that allows you to track the battery life of your friends’ devices. In turn, it also lets your friends check your devices’ battery life. This way, you can make sure that none of you runs out of battery in case of emergencies. This tool also has a feature that allows you to chat with other people anonymously.

The best thing about this is it does not cost a single penny. All you have to do is download and install this free app on your phone or tablet. It is available on the Google Play Store.