Carat is Free to use & available for iOS & Android devices including music players. You need to download & install the App on the device whose power you want to monitor. You need to occasionally operate the App like any other. Carat starts monitoring your phone's energy usage. It takes readings of your device intermittently. These are then sent to the servers at UC Berkeley & the data is analysed. Once done, the response is sent back to Carat with an "action to be taken" report for the user.
Obviously, there will be some hesitation in the minds of potential users of Carat on privacy matters because of the App's very nature. The research team claims to have a very clear Privacy Policy. It states that it does not collect any personally identifying information: no names, no email addresses, no private data from other Apps, and so on. Although Carat does try to detect whether users are moving around, it doesn't record their absolute location.
Carat, says the team on its Website, is a research project, so it reserves the right to publish results Online & in academic publications, & the right to release the data sets into the public domain, without identifying the user in any way.
You may click here to download Carat on your iOS device
You may click here to download Carat on your Android device
Since February this year, a team of scientists & research scholars from the UC Berkeley have decided to tackle this "energy crisis". The aim is to find & fix "energy bugs"- Apps that unnecessarily consume power. The team has come out with its own App called Carat for this purpose. 
