This amazing new technology called Layar is currently available on Android devices, but is supposedly being developed for the iPhone 3G S as well.  What is it?  Point your phone at a location and see what it's all about.  For example, you're on a city street and you want information about the 4 restaurants in front of you...point your phone at 'em and check out the info as it's overlayed on the preview your camera is displaying!  Great looking demo in the video below.  I want one.