Reviewed in Android Features Wishlist
Battery Status Indicator along Statusbar: This app displays a thin line (of chosen colour) along the top edge of the screen, varying in length with battery left. There's a neat little charging animation too. If this were to be incorporated into any variant of Android, I imagine that it might look out of place. But, it is a much better visual indicator of battery life than the usual miniscule battery icon in the status bar.
WilliamMRees - Shows a subtle bar at the top most of your screen indicating your battery life. Its always nice to have a quick glance if you're in the middle of doing something.