Is it possible to add a simple input jack to your car stereo in order to play your iPod?

Some radios have RCA inputs in the back that would let you do this, but most do not. Your best bet is to get a wired FM Modulator. After installation, it allows you to plug your ipod directly into the FM antenna and is world's better than transmitting FM from the device to your cars antenna wirelessly. Once installed, you could put an input plug in the dash to conceal the hardware and make it easy to use your player.

I found the best thing since sliced bread...http://www.crutchfield.com/S-9oDEWuNVIo6/cgi-bin/prodview.asp?i=142FMMOD01 It's not wireless so there's no interference. Not to be confused with an FM transmitter. Basically it adds an AUX input to ANY radio. No searching for a clean channel. It feeds your audio signal from a headphone jack ( or RCA cables) by FM modulation, directly into the antenna input on your radio bypassing the antenna when on, allowing the radio to work as normal when off. It comes with an On/Off switch. This is the answer. Totally versatile. Here's one in action - http://www.youtube.com/watch?v=MHBI0LBGhR0

can be done. If you dont have experience with car audio then you should take it to your local car audio shop. You will have to pull the radio out and do some wiring. The other 2 comments are correct but it sounds simple if you do it everyday.