I love the way you can plot people's movements via bluetooth, but it's also the reason I turn my own bluetooth off.
I wonder if there's a need for something that broadcasts like bluetooth does with minimal power, but allows you to change your identifier at will instead of relying on your MAC address. An app on your phone would let you configure how often your token rotated, or to not broadcast at all. The problem that I see with this is that nobody would install the app because it provides no benefit to them. Maybe that's what's missing, such tracking needs to be beneficial for the customer but at the moment it benefits only the retailer.
I did work on a project concerned with tracking via Bluetooth a couple of years ago. Depending on the way you try to locate the mobile devices one advantage of Bluetooth can actually be its smaller range compared to a Wifi AP that's running at its full range.
With regular consumer hardware it is basically impossible to use signal strength indication between an AP and a mobile device to do any kind of serious range estimation. Your best bet is therefore to use a whole grid of APs. The easiest way to locate devices is then to run all of them with a limited range and locate mobile devices based solely on proximity to a single AP. A more complex but potentially more accurate solution would be to run them with larger overlapping ranges and calculate the mobile device's location based on the intersections. Running too many Bluetooth APs that actively broadcast for peers, however, may have the unintended side effect of jamming the 2.4 GHz band.
All in all, I actually agree that Wifi is the better solution nowadays. Symbian was the last smartphone OS that had Bluetooth set to visible by default. Since the switch to Windows all of the major smartphones will be invisible by default which was not the case in former years. Also, quite a few smartphone users will have Wifi enabled at all times which means their phones will actively broadcast for networks which makes them easy to track in a passive way using hardware that is already installed.
I don't know about France, but in the US I never use Wifi, since often I have to go through some stupid sign up page to actually use it and my LTE cell data is usually faster anyway. I might have my Bluetooth on, though. So the number of people running Bluetooth may be higher than those running Wifi.
If people only use the Wifi for a function like the guide it might skew results to only use WiFi as well since you'd only be measuring a certain type of user.
I wonder if there's a need for something that broadcasts like bluetooth does with minimal power, but allows you to change your identifier at will instead of relying on your MAC address. An app on your phone would let you configure how often your token rotated, or to not broadcast at all. The problem that I see with this is that nobody would install the app because it provides no benefit to them. Maybe that's what's missing, such tracking needs to be beneficial for the customer but at the moment it benefits only the retailer.