I wonder if anyone has made an implementation of this as a low-cost indoor positioning system for a smart home. Maybe with some simple beacons transmitting at a

I wonder if anyone has made an implementation of this as a low-cost indoor positioning system for a smart home. Maybe with some simple beacons transmitting at a certain frequency, and the phone receiving, processing that and updating its estimated location to a home server. It probably wouldn't be precise enough for a definite location (and room-precision is usually enough), but coupled with other approaches... __________ = The frequency range would probably have to be pet-safe, since dogs and cats can hear way higher frequencies that we can't.