Btw, your suggestions make me think of another interesting approach that local governments could take. Instead of devices reporting themselves, we could have h

Btw, your suggestions make me think of another interesting approach that local governments could take. Instead of devices reporting themselves, we could have hotspots observing mobile phone signals (eg. integrate them into traffic lights): we'd need at least 3 nearby for triangulation, and they'd have to be everywhere, so it would require government support and desire to provide traffic info for the public.