The concept would allow iPhone users to locate paired Bluetooth devices, which would then emit a high pitched sound or light. Apple even suggests that this idea could be used with a tiny Bluetooth device that would be attached to almost anything such as keys, wallet, etc. An interface on the iPhone would then be able to locate several devices at once!
"The distance between the devices can be calculated by comparing the amount of time delay between the transmission of the signal sent from the master device to the slave device and the reception of the return signal from the slave device," Apple said. "With a precise timing system, the master device can be capable of performing such measurements. Since the speed of the radio waves is known, the distance can be calculated using the time information".