I have just published my first little Android application: AndroHUD - A heads up display (HUD). It's really just playing around with the sensors a little bit, but the application also has some useful features:

AndroHUD is a simple heads up display (HUD) which displays your speed, heading, altitude, pitch, roll and the current g-Forces. You can activate a mirror mode if you want to put it at the dashboard of your car. You can also configure speed warnings: The HUD will warn you when you exceed certain speeds.