This cable would do it.
http://www.monoprice.com/products/pr...seq=1&format=2
I was trying to find a shorter one since this would be under the console.
There is one catch which is that there is a video cable coming out as well. What that means is that the iphone will think that there is video through the dock connector, which can sometimes be trouble if you are trying to view something while driving. I never attached the video cable when I had it. I never had any issues with this on mine because I never tried to watch anything while I was driving. =)