The new iOS and Android app Carat promises users better battery life by delivering tips on how to conserve energy. According to TechCrunch, the app was designed by a " top-notch" team of "M.S. and Ph.D scientists from the UC Berkeley electrical engineering and computer science department’s Algorithms, Machines, and People Laboratory (AMP Lab)."
The free app uses gathered information from your device to decide what apps are hogging your iPhone's battery power. To do this the app has to take "measurements" from your device. This means you will need to allow it access for it to work. It also takes a few days to collect data before it can start sending you battery saving tips. So don't expect instant results.