My stock RBK radio doesn't have an auxilliary input. I tried the FM modulator for a while, but over a 30 mile commute I have to change the frequency several times. I bought an adapter that plugs into the back of the radio where the CD changer would go, and provides two RCA inputs. It works great for iPod and satellite radio. Anco Auto Specialties
I put a similar one into my girlfriend's Liberty, but that one has an iPod connector. I prefer mine because the factory radio doesn't give you much control over the iPod, and with the auxilliary input you can plug in anything.