If cell phone radiation emissions is something that concerns you, you may be interested in taking a look at the Pong radiation-reducing case [$59.99- Web link].
Pong Research was nice enough to send us a sample to check out and, at first glance, it looks like a solid silicone case. It offers good protection while giving you full access to all ports, controls, and the camera. But a quick look on the inside reveals what makes this case so valuable - the Pong Gold PCB Module that reduces overall radiation output by 60%. It is this PCB module that directs a users iPhone’s cell phone signal and radiation through the back of the phone keeping it away from the user's head.
While the price is not cheap, if you are in the market for a silicone case and want protection from radiation, it's worth a look.