Android 2.1 Live WallPaper

Trying to achive something similar to a Doom Live Wallpaper ( [login to view URL] ) however I will be using my own graphics. There will also be some gameplay elements involved, such as health, Item pickups, and the ability for the user to directly "help" out his avatar in certain situations by tapping on him. The avatar will engage enemies at a constant rate, and will be smart enough to switch out items once they are completely depleted. The avatar will also seek out replenishment items if one is available. The avatar will do this indefinitely, even after death, the Avatar will re spawn and continue with the process. There will be different animations for each weapon as the avatar walks, runs, attacks, and fires. The scene will be compromised of several buildings that at this time have no real use other than aesthetic, however the buildings will serve as a boundary where the avatar cannot go past. (obviously) The app needs to be somewhat battery friendly.