This really depends on what kind of testing you have in mind.

You can try Win32::GUITest, not sure if it also works on Windows mobile.

If all else fails, you can still get a bunch of Lego Mindstorm stuff and use LEGO::NXT to automate testing "from the outside". Sounds crazy? Well, so does solving a rubik's cube in 5.3 seconds with only a phone and some Legos...