Admittedly, these iSimple GateWay kits only work with certain car makes and models, but still--if you are looking for a way to connect your iPhone or iPod into your existing factory car stereo, you might want to consider one of these (universal options available as well). I also enjoyed a brief demo of their IS713 WiFli transmitter--The WiFli works via an iPhone app that makes the transmitter search for an optimal frequency to transmit on.
Wifli Control
