A free app for Android, by AntTek Mobile.
Battery Stats Plus is a utility that helps you to monitor the battery level of your mobile device in real-time, allowing you to make sure that it never runs out. This is accomplished by tracking the usage of each individual application, and by collecting and analyzing the data from each of those apps.
These data include how much the app is using your phone’s CPU, network, and sensors. This tool also tells you which apps are using the most battery power. Additionally, it has a cloud-based service where you can compare your battery usage with other users.
This utility works on Android 2.2 and above and requires root access to work properly.