hardware and ideas, 95% of which were never going to make it into my car. All I ever use on a daily basis is Pandora, maybe an occasional mp3 (if I'm feeling nostalgic..my collection is that old) and the occasional search app or OBDII app. The tablet is more than capable of handling all that, and like you said, all the hardware AM/FM/HD radio and Bluetooth is handled by the Kenwood. The Bluetooth OBDII dongle talks to the tab, and the Droid provides the 4g connection for Internet access.
As for plans....that's for another thread.