This is an Android "Live Wallpaper" that runs a Cellular Automata simulation - often called "Life".
The rules it uses are taken from: Conways Game of Life
The animation runs in the background on your Android device, updating the screen every generation. You can set how big each cell is (default is 8 pixels) and how long each generation takes (default is 200ms).
If you end up with a generally static or dead array on screen, you can triple-tap the screen to reset to a random population.
It's free on the Android Marketplace: Life Wallpaper (link will probably only work from your Android device.)