The 4S was the first iPhone to support low-energy bluetooth. Note that this use-case is handled specifically in the spec: http://en.wikipedia.org/wiki/Bluetoo

The 4S was the first iPhone to support low-energy bluetooth. Note that this use-case is handled specifically in the spec: http://en.wikipedia.org/wiki/Bluetooth_low_energy#Electronic_leash http://en.wikipedia.org/wiki/Bluetooth_low_energy#Electronic...