This is something that I'm personally very interested in... I have a Nexus 7 tablet, and after it upgraded to Android version 4.2.1, the battery life was just awful. After 4.2.2, the battery life would just randomly decide to go from 100% down to 10% over a couple of hours while sitting on the table, unused.
The problem, after doing a lot of research, was a wakelock that something was holding. After a ton of app upgrades, the problem mostly went away. But even now, I'll occasionally come back to the tablet and half the battery has drained in just a couple of hours.
Definitely going to try this app and see if I can track down the problem.