Bluetooth LE (BLE) seems to be all the rage right now with many proclaiming it an NFC killer and the future of both, indoor positioning and pervasive service interaction. Key in this context are BLE “beacons” that broadcast information about an object or place. Mobile devices pick up this information and – via signal strength – can estimate how close they are to a beacon. By triangulating closeness to a few beacons, devices can then calculate their position in space. Furthermore closeness information can be used in the context of proxemic interaction , where devices display different information and interaction options depending on how close you are to a point of interest.
 Check out the Jan-Feb 2011 issue of Interactions “Proxemic Interactions: The New Ubicomp?“
Some BLE beacons available today: