Shades of the RFID world to come -- when one knows a great deal about things in the physical world (RFID tags on mountains?). Years ago I wondered about bar coding journal articles, so I would look up the information online rather than enter it into my article database.
This app takes that idea MUCH further. They use the bar codes already on books and objects as a unique identifier to join the physical item to online data. Of course, as with CD track databases, consumers will build the data as they scan. You can use an iSight camera or a USB scanner to read the bar codes.
Very, very interesting.