Few people realise that there are companies that do this, nor that they are simply tracking the Bluetooth beacons in phones, fitness trackers and even sat navs.
Works quite well.
It'll get worse in future, as things like smart locks and other devices demand a fixed MAC or other identifier to allow access! (And of course, that's a bad way to deal with security, and since developers are lazy...)
IPhones now scramble their wifi identifier iirc, & Bluetooth will be too - at least that's why at least one smart lock removed the "door unlocks as you get near" feature. But who knows?