One of Battery HD's most interesting features keeps you informed of how much time the battery will last while using different applications. For example, you can find out the exact amount of time you can listen to music or watch Youtube videos.
Battery HD is one of the many apps that you can find on Android to monitor the duration of your battery. It's important to keep in mind that this app won't magically make your battery last longer. Rather, it'll simply keep you informed of how much time it has left.