It needs a camera to provide "reality" images onto which themed icons can be placed in relation to the distance & direction to the item being searched for. Works best out of doors - more accurate. I've found it useful for finding nearest bookstore in a city centre and also direction of nearest train station. You look a bit odd when you are using it - like you are taking a really long time to take a photo.....spookiest list I called up was to plot distance & direction of people who had recently sent tweets.
robotvision is a good one aswell, i've been switching between acrossair and robot vision. robotvision kinda has a 1up because it can find flikr uploads and tweets if you're that way inclined.