Synchronous Gestures
The appeal of synchronous gestures is so widespread. One cool result of its correct implication in devices with rear-mounted cameras is the creation of shared augmented reality. On the displays for all of the synchronized screens could be the video of the space in-between them with, for example, the addition of a public figure giving a speech. Depending on where the users are, they could see different sides of the three-dimensional augment reality. Another interesting idea would be to use this synchronization for musical purposes. For example, If it was easy to synchronize 3 iPhones together, you could create a more usable interface, like a full length keyboard or a more in depth display of current looping waveform.
Group Coordination
In this paper cellphone proximity is detected through the use of on-screen markers. While this is a novel idea, it seems to be a too cumbersome to be used in most situations. First off, this technology requires a camera for tag detection and for the tags to be displayed, which would need to be on the display as long as the device is tracked, even if the user needs to use an application without these tags. On top of this, this technology can only be directly applied to devices that are used with their screens pointing up at the camera, like a tablet or a cellphone. With that in mind, the ability to create your tracking tag on your phone without any added hardware is of great appeal. Maybe with a camera array these tags could be used without displays being limited to pointing in a single direction.
