Alternatively, some kind of wifi/3g blocker or jammer, could be the answer.
In some ways it might make sense to use a polite version of that, where devices would 'hear' a wifi SSID signal, or whatever, with a 'this is a private place, no creepiness, please' signal embedded in it. To stop denial of service, or only having official jamming, you could have that privacy signal location specific, with a Lat/Long GPS position, and then the whole thing signed against a central server (probably google, but a non-Profit would probably be ideal), so that people couldn't wander around with portable jammers.
Then shopping centers, schools, private homes, resturants, etc, could easily register for a code, plonk it on a jammer or other wifi router, and behold, an illusion of privacy.
If there were government regulation about devices having to obey such signals to be legal for use, then I could see it working.