I got an entirely new head unit for my car... I can switch between AM/FM radio, XM Radio (which I'd had a subscription to previously but was using a separate tuner), my iPod, CDs and there is actually another auxiliary unit still open.
My iPod simply sits in my glove compartment, runs directly through without FM transmission and i can control it through my stereo or the little remote it came with.
I love it so much and it's so simple and seamless.