Apropos my recent discovery of camera heading in iPhone metadata comes word of a petition for Apple to create functions that would allow Augmented Reality development on the iPhone:

http://gamesalfresco.com/2009/07/02/open-letter-to-apple-let-us-augment-reality-with-the-iphone/

Augmented Reality are applications that combine computer-generated imagery (or text) with imagery generated from a camera. Examples include applications that show historic photographs from your current vantage point, identify significant features in the landscape (buildings, mountains, constellations), and games.