Time for the usual disclaimer, since we're taking a journey into the murky world of Cupertino's patent applications -- it's just as likely we'll never see or hear of this tech again as it is to wind up in the next iPhone. While everyone else is betting on NFC, Apple wants to use next-generation cameras and invisible ink to negotiate digital handshakes. Snap a picture of a cash register with a barcode and your iDevice will generate a unique ID to pair up -- but in order to keep the technology secure, the codes would have to be painted on with "invisible" fluorescent coatings. When you're pairing two iPhones (for example) to share contacts, the key could be generated on one of the screens while the other took a picture of it. If this all seems too complex, boring and pointless now, just think: this could be how we log into Foursquare in a decade's time.