I have a USB GPS plugged in, and it's currently sitting on the right side of the rear deck. I don't have the microphone installed yet, so currently you would have to pull over and type in your destination. I also have a copy of Microsoft Streets and Trips that works with this USB GPS, but I have not loaded it on the PC yet.
I also have a digital I/O board to install, with 16 in and 16 outs, and each out can drive a 2A load common collector mode. The I/O is integrated into the Driveline front end software, so I can modify the code to turn things on and off by which screen I am on or by status of input bits, etc.
I also have a 6 port intelligent USB hub that I am going to mount in the cup holder area so I can plug in a USB volume control knob, and thumb drives, and charge my phone, etc.
There's lots of room for expansion.
You can install a Mac Mini, and run it off the intelligent DC-DC converter. It's output is jumper selectable up to 24V, I think the mini uses 19V? There are guys doing it.
If you see it, get it, for tomorrow it may be gone!