Re: Bluetooth? Really?
You read the signal strength and make very bad guesses about how that maps to proximity. If Bluetooth was in any way predictable or reliable that might work. Might even be able to self calibrate by tracking beacons move in and out of range. If it was predictable.
My experience of Bluetooth between phones is serial, random failure. Radio reception usually defies understanding in the busy environments this needs to work in. Seems designed to fail, theatre not solution. The UK version is so inept probably best to have it die quickly before wasting more human resources.