I was recently recommended Wikitude by a friend, so I downloaded it off the Android market place, and fired it up. It's a little slow to start, but it's something really special once it does.

It uses a combination of the inbuilt compass and GPS receiver to locate your position and facing, then it searches its content database for points of interest around you.

It's pretty cool seeing the technology convergence on a Google map type interface, but once you fire up the 'camera view' then it really comes alive. It overlays the same points of interest onto your camera viewer, giving you information about each as a pop up when clicked on.

Developers' site is here: http://www.mobilizy.com/en/wikitude-ein-reisefuhrer

It's a really impressive integration of technology into real life, which actually has a valid use. On the down side it takes a few seconds to load, and if your GPS setting is off then it's not that accurate, but that's not really a Wikitude issue.