on the Droid, I forgot what it is
i dont believe there are apps that will help you with this but it's more of a how do you conserve battery power.
like the above post suggests, get the widget, it will help you turn off unnecessary battery consuming programs like bluetooth, screen dimmer, gps, and wi-fi. all these consume a lot of power and if you aren't using them while you sleep, then you should turn them off.
also settings>accounts&sync>background data (deactivate) will save you battery power too (it even tells you) and when you need it activated for any program, dont worry, the app will tell you that you need to activate it and when you choose "ok", it takes you directly to that page to activate it.
also to conserve battery power please dont feed it past midnight, and please dont get it wet.........