harman kardon do a kit called the idrive it connects the stereo to the ipod and gives you a seperate screen and controller and allows the ipod to be tucked away and charged at the same time.
I have had one for about a year now, Sounds2K had had a couple, they are about as good as it gets without goign to the point of buying a stereo with an ipod connection.....and then you lose the bose
they are advertised frequently on Ebay as well, cost about £50
alas sounds2k will be selling car soon, ive fitted one in my car and was a little disappointed with the results, works well but the sound is distorted on mine, lots of hiss and anything with sssss sort of sounds, just gets destroyed, it does have a line output and i was thinking of wiring it in place of the cd changer, as that outputs at line level. guess it would be easy enough to do, just needs a switch in line.
anyway fitting is OK but can be a bit tight behind the console as there is another little box to find a place for which has the radio tx in it.
i guess that you could wire a small pre amp inline with the sender unit but then thats more work and more stuff to hide.
anyway in short, great idea, just a shame that teh audio is a little sketchy.
cheers
nathan