[janekm]

There are very promising "ultrawideband" solutions (allowing distance to be determined from time of flight of a message rather than signal strength) but the use cases are limited as there is no existing infrastructure. The best that can be done on phones is "sensor fusion" from all available sensors (including wifi and BLE, also integration of motion data) but it requires very extensive mapping of the location in advance. iOS suppports this since a few releases ago but only for locations that have been mapped by Apple so the use cases are rather limited, presumably the mall/airport feature just shown used it.