My experience was that the RSSI does change reasonably consistently, but that there's quite a lot of noise (so you need to smooth it appropriately). I also get

My experience was that the RSSI does change reasonably consistently, but that there's quite a lot of noise (so you need to smooth it appropriately). I also get the impression that it's affected by orientation of the phone relative to the beacon, and also by anything blocking line-of-sight (including humans). Mounting the beacons high up could reduce the effect of this last point.