I agree that this seems like a good idea, but you'd still have to upload, so you'll need an actual computer processor and controls to access the harddrive and to put files on it, etc. Maybe that computer should be removable so you could take it into the house. Maybe is should be really small, portable. Oh yeah, that's why all of the fancy cars have systems that will run an ipod. Since you've already put on the songs on it, you can keep it up to date more easily and you can move it from one car to another, etc. Car makers don't need to be spending their time and money designing stuff that's already designed.

They made them about 10 years ago. The iPod came to market about then though, and took over the market.

sony makes a couple models with solid state memory built into the face-plate, just pull it off, bring it inside to the computer and download, when you put it back on you can play. if you've been waiting and looking for it, your just not very good at research.