Totally newbie: some doubts about BeaglePod project

Hi everybody.
I’ve found BeaglePod on the web and I’ve found it very nice, but I can’t understand some things, may anyone help me?

So, BeaglePod is a replacement as iPod used for “iPod ready” car stereos?
Link is made through Apple Accessory Protocol, but I’ve seen it is a serial protocol.
Several car stereo (such as Kenwood KIV-700 or latest SONY products) has got USB port to connect to iPod (through USB to iPod connector cable).
So iPod USB cable is it just an USB-to-serial converter?

Thanks, Michele.