I believe this is one of the main reasons why the device itself doesn't have a data connection. Think of it as wearing one of those bluetooth earpieces that you pair with your phone.
Probably not since it doesn't have a 3G radio, but not sure how safe or healthy the bone audio conduction is. I hope Google knows what they're doing there.
That's far from proven. There have been a variety of inconclusive cell phone studies, but definitely none about having a 3G radio glued to the side of your head and active for most of the day.