A bit of a parlor trick but still interesting as a proof of concept is the easter egg in Yelp’s iPhone application.
After launching the app and shaking my phone I saw a heads-up type display containing an overlay of restaurants and bars down the block. Turning about and pointing the phone in the opposite direction loaded watering holes towards the East.
Another AR app for the iPhone is one for the Metro in Paris but none of this is as cool as AR for contact lenses.