I see. In theory, like any idea, sounds cool. I've actually taken real world pictures around my building to mockup a possible UI sometime.

The issue is that, as far as i know, geo-location (GPS at least) has a +-10 meter precision, so placing content at a specific spot is, fuzzy.

ps.: by placing content at a specific spot, i mean grabbing the latitude/longitude/height and possibly direction from the device and allowing anyone around it to see it by pointing a device (smartphone/tablet/glasses) there.

edit: of course, the precision is really an issue depending on what your'e "tagging". If you're adding stuff to a town square, +- 10 meters don't make any difference :-)