So while I am not convinced the infrastructure costs and so on are going to happen any time soon the physics of these in floor charge systems is quite well understood. They have a coil which only transmits any energy when there is a sympathetic resonance coil in the right place (a car). The electromagnic field will be tightly linked between them for all sorts of reasons not least efficiency and so not to make a mockery of EMC regulations (dodgy radio waves disrupting permitted equipment like a radio). In fact it will be those factors which make them so difficult to make. They won't be a hazard to a body of any kind. As an aside, phones are close to microwave (as in cooker) but still a country mile from causing heating resonance. Charging coils even further away.