Michael_Curator writes to tell us that mobile phones now have a "reality overlay" app that combines a smartphone's camera, GPS, and compass to augment a user's view of a particular location with metadata. "It works as follows: Starting up the Layar application automatically activates the camera. The embedded GPS automatically knows the location of the phone and the compass determines in which direction the phone is facing. Each [commercial] partner provides a set of location coordinates with relevant information which forms a digital layer. By tapping the side of the screen the user easily switches between layers."