I think technology exists that could make that part of the concept work, but it would require certified transmitters that automatically check in with a database

I think technology exists that could make that part of the concept work, but it would require certified transmitters that automatically check in with a database daily or hourly. There's also the issue of radiation danger. A human can not be close to a high (or medium) power FM antenna for any length of time without adverse health effects. And a human can't really be around a low power FM antenna (i.e., 10-100 watts) for extended periods. The health issue would be a problem with the "wild" idea. New Zealand has a popular service like you mentioned, but the limit is 1 watt. But in many cases, that can cover a town.