Apple has inked a deal with three major car manufacturers today to make it a bit easier to connect the iPod into car stereos. Apple has come to agreement with Ford, GM and Mazda to see that 70-percent of their 2007 model vehicles will offer some way of connecting iPods directly. The iPod integration seems to be as simple as a dock connection in the glove compartment. iPod control and navigation will be done through the already existing stereo controls. GM has already announced pricing regarding this issue. As early as October they will offer the iPod audio connection for $160 plus labor. I'll stick with my cheapy FM transmitter and 12V DC charger thank you very much.
I work for the company that's building these head units and we're actually integrating the circuits into the PWBs now. The "labor" involves plugging the cable into the back of the head unit. Ford and Mazda at least will be offering it as a factory option out the door.