Even the process of pairing the two devices is novel, says Nicholas Palmer, who developed the game with Kemp and colleagues Thilo Kielman and Henri Bal. The pairing process takes place before the game begins. First, one phone generates a bar code that encodes the phone's IP address. This bar code is displayed on the phone's screen. The other player then uses their phone to take a picture of the bar code--in essence, scanning in the IP address of the phone. "This pairs the two phones," says Palmer.

While these sorts of innovations help to extend augmented reality into the mobile gaming arena, the real innovation here is the communication system.

"There are a lot of situations where you would want to start interactions quickly between phones and mobile devices," says Morris Sloman, a professor of distributed computing at Imperial College London, in the UK. Such a system could be particularly useful for military operations. Currently, there is a trend toward using Internet-enabled phones in the military, but ideally phones could communicate with each other even in areas where there is no infrastructure. Such a system would also be useful in disaster relief efforts, when infrastructure has been destroyed.

But Sloman questions whether a commercial system will be reliable if a Wi-Fi connection is not available. "In Europe, many service providers will not allow incoming data connections on their 3G networks." Although outgoing transmissions are allowed, incoming data usually has to go through the network's secure servers, he says. Palmer and Kemp accept that there may be issues with different network providers.

Photoshoot will be presented at the Mobile Opportunistic Networking workshop in Pisa, Italy, next week, and should be available to the public in the next couple of months. But in the long run, the hope is that its underlying ad hoc network capabilities will find broader use, says Palmer.

There are other possible ways to allow mobile devices to pair and connect, such as the protocols Bonjour and Universal PnP, says Blair MacIntyre, director of the Augmented Environments Lab at the Georgia Institute of Technology in Atlanta. And similarly, the iPhone app Bump allows pairing and information exchange between multiple devices on an ad hoc basis, just by bumping them together, he says.

However, Bump still relies upon remote servers, says Kemp. And both Bonjour and UPnP only work within a single Wi-Fi access point.