The Digipower FM-CS100 2-in-1 Bumper Case with Built-in FM Transmitter protects your iPhone 4/4S and lets you transmit sound wirelessly to any FM radio. The FM transmitter is built-in to the polycarbonate and silicone bumper-style case, and it works with worldwide adjustable frequencies. With the case, you can charge your iPhone and a second device while you charge the FM transmitter. You’ll be able to make calls and access the iPhone’s controls without removing the case. There’s an app in the iTune’s store, called FM Bumper Case, that gives you touchscreen control of transmitting your music to a nearby radio. The case is $59.99 at The Sharper Image. Amazon seems to have the same case for $37.46.