title: Is iPhone Proximity detection possible with Bluetooth?
body: <p>Would it be possible to fill a building with 20 - 30 bluetooth devices that act as proximity detectors and write an app that can calculate location in the building based on distance from the current detected sensors.</p>
  
  <p>I've looked at the GameKit API, but I don't see anything about calculating distance from devices.</p>
  
  <p>Can someone point me in the direction of an Apple API, or a 3rd party API that can be used for this kind of application.</p>