Android -- How can we determine the Battery Usage statistics per application?

I am having trouble finding a class or API in Android documentation that would help me get battery usage statistics per application.

I have read PowerManager and BatteryManager classes but they are of no use.

However, I can find applications like Power开发者_运维百科Tutor that do provide battery usage statistics per application, so I think it's technically possible.

Can any one point me in right direction?

I'd be surprised if such an API exists. Rather, I expect that PowerTutor is using some sampling heuristics to estimate how much of the current battery usage to blame on each application.