It occurs to me that maybe a better approach to AML via WiFi is to enhance the WiFi standard to include location information, either in the beacon frame or in another existing frame or in a frame specifically for location information. (I dare say that vendors can already do that by including proprietary Information Elements but that is exactly the solution that we don’t want.) The operator of the Access Point would have the option of disabling the transmission of location information.
The privacy implications would be less severe, as no massive database is needed, either secret or public, and you can opt out easily enough, and updates are handled more cheaply when an AP is moved.
I note in passing that a network of Cisco Access Points is capable of locating a given wireless client using triangulation on the Received Signal Strength Indication (RSSI) i.e. works the same as multiple cellular towers doing it but more accurately. I don’t know whether other vendors have the same functionality.
Doesn’t help if you are at home as I would guess that most people don’t have multiple Access Points (and if they do, the APs might be different makes/models that are not capable of cooperating in that way).