Battery gives you a number of interesting stats such as how long it will take to fully charge your phone. The first screen tells you how much time you have left to run a certain task before the battery dies. If the app is telling you that you have just 10 minutes left to watch YouTube, you know which clips you can view and which ones to avoid. The app will even estimate how much talk time you have left for a conversation over 2G or 3G. Knowing this data can be important, especially if you are using your iPhone for business. You don't want to be on an important phone call with Mr. Drysdale from the bank when the battery on your Apple iPhone dies.
Besides giving you enough stats to help you make an informed decision on how best to stretch out the battery life on your iPhone, the app also will give you tips and recommendations such as reminding you to turn off Wi-Fi when you're not using it, or telling you that reducing the brightness on the screen will help enhance battery life.
The Battery app is available as a free download from iTunes and is available for the Apple iPhone 5 and Apple iPhone 4S. Make sure you have enough battery power left to downland the app on your handset.
source: iTunes via RedmondPie