Playing Ingress, by Google spin-off Niantic, I notice that the XM dots away from portals tend to be persistent and only over certain houses and locations. It looks a lot like it’s based on wifi activity, picked up in scans by Google camera cars. (The sort of thing Google got in trouble over.)
Naturally they also have my phone location while the app is running.
Time to think about all those apps that stay in touch with the mothership.
