Griffin Itrip Auto Universal Plustransmitter, Play Mp3 Player

I tried it once and it worked fine, as long as you were in range of a strong FM station.  As you drive further away, and lose that station, you lose the MP3 playback.  So...if you're near an FM station it works great. I live in a suburban area so it didn't work great for me.
Description Griffin iTrip Auto Universal Plus Fm Transmitter for iPod iPhone Smartphone Compatible With Any Portable Audio Device With A 3.5Mm Headphone Jack Charges Any Portable Device With A USB Port Built-In Antenna Powered By 12V Power Outlet FM Stereo Modulation Listen to your MP3 or other portable player on your car stereo 12V power plug works with any cigarette lighter socket Simple 3-step setup Lighted display is easy to read Built-in USB port lets you charge your player using your own charging cable No international shipping.