That's a good point about GPS. It probably doesn't ever work indoors, and it may not work outdoors.
Your "not kill grandma" might or might not work. It depends on the shielding of the monitorning device, and the sheilding on the (putative) wsd, and how sensitive the lo of the monitorning device is, how much rf power the (putative) wsd puts out, antenna/lead orientation, grounding. Hey, if we kill a few grandmas, it might be good for a few inheritors (after they get over the fact that they killed her.)
Prevent use near a hospital or make it difficult for anyone over age 15?
So, we devolve long and latitude exactly how when indoors? When I go on Earthlink at my mother's house in San Diego (she gets DSL and phone from earthlink), and then visit my web site, it tells me my physical location is in Los Angeles, specifically out of LSANCA 54, which is the switch where Covad provisions out DSL service for Earthlink customers in San Diego.
Of couse, the CO serving my mother's house is SNDGCA, indeeed I think it's ULLI is SNDGCA54. So, a (putative) WSD that used information from my IP address would prevent me from transmitting on channels 2,7, 9, etc. However, those channels are usable in San Diego (most civilized areas), but this won't prevent me from interfering with local channels.
We'll just have to trust the users to accurately know their location, just like all those (formerly) infringing users of DIshNetwork reported their locations for local-into-local. Or, they reported the locations that they wished they were at. Either case, it will ony interfere with tv reception of others and possible loss of life.