Application to know the amount of remaining battery There are many, it will consume the battery most apps reside.
Are consuming the battery even when you're not looking at the screen to become concerned about battery power. It is putting the cart before the horse s.

Nonresident is a very simple application that displays the remaining battery power only for one second, when you launch this app.
You can check the battery and then immediately tap the icon If you place a shortcut to the home screen.
When not in use does not consume the battery of course.