Pretty slick idea. I have a couple N7's and have considered replacing the stock HU with one. I have considered placing a single din HU in the glove box or up dash and hooking into the aux inout and using the the axxess aswc for volume and source. A guy on Nasioc is doing it with a rooted kindle fire running cm9.
my NEXUS 7 (formerly kindle fire) 'headunit' COMPLETE - NASIOC