There are a bunch of car stereos out that let you plug your ipod or iphone into them to be controlled by the head unit. But I've been googleing and can't find anything that works the other way around.
Is there any way I can hook my ipod/iphone/ipad up to a car stereo and control its functions through the ipod, instead of the other way around?
I was driving in my friend's Acura and his factory navigation screen had full control of the stereo and navigation and everything.

I basically want the same thing, but utilizing an ipad as the head unit.

Somebody's gotta have something like this right?