Something that could help if you are looking at how Ants was done is to look at the source for Dock:
cre.ations.net - Creation: Dock 3.0: Quick app switching for jailbroken iPhone 2.0 phones
It runs in the background and displays over other programs - there was a special mode required for this to work, and the limitation used to be there can be only one program of this type.
Now he is using the WinterBoard module that allows injecting code into SpringBoard.