There are products like the Monster iCruze
http://www.monstercable.com/icruze/
or PIE Adapters
http://www.pie.net/index.cfm
They are all preety pricey.
Honestly, I'd recommend you put in an aftermarket stereo that has an aux in. It will cost about the same price as one of those adapters and function a lot better. I just put one in the Rubicon that plays MP3 CDs and has an aux in for $129. I wanted to stay as cheap as possible, but still have all the functions, since radios like to disappear when you have the soft top on
In any case, check out your options on
www.crutchfield.com for aftermarket stereos and factory aux adapters. I stand by them as much as possible becuase they give you everything you need as well as detailed vehicle specific instructions. If you buy a stereo $129 and up, you even get your dash adapter and wiring harness for free - they would cost over $40 at the big boxes.
Hope that helps.
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2008 Unlimited Rubicon - 3.5" AEV/Nth lift - 35" MT/R with Kevlar - AEV Wheels - York OBA
2008 Patriot - Fuel Saver