Audio I've got taken care of with a little box of tricks that interfaces my standard HU with my iPod, so this screen will really only be used for GPS and reverse cam, and possibly bluetooth for my phone, if it's any good.

I did look at Android tablets but the two problems I've got is;

1) finding one that has an AV input (for the reverse cam), and it needs to autoswitch the AV channel both on and off with power/video signal

2) Getting one that isn't too big, and doesn't need any external buttons. The screen size on the housing is exactly 7", and finding a 7" screen Android tab isn't exactly hard, but finding one that the has a small enough screen surround is the tricky part, as if it's too big it won't physically fit inside the housing (the one I've got is pretty slim, and even that only has at most a couple mm top and bottom play, and probably 2.5-3mm side to side play. Almost a perfect fit!). And if it needs external button presses, like a home button or whatever, I won't be able to press them, as the cut out is only 7", and I really don't want to spoil the looks by cutting out a notch to press a button.

Data would be cool on it, as then I could run Google maps and tether it to my iPhone for internet, but at the same time, half the reason for going to way I've gone is to get a full "offline" map package, so that if I'm in an area with no cell data, the sat nav will still work (whereas Google maps, and Apple maps for that matter, just goes blank because it's constantly "streaming" it's maps over cell data. (Plus, I could run the TV Catchup app, and get BBC News 24 going on ; ) )

But there's always the future - this is really just a test to see if it can be done and all work fine, then I'll get another GPS tablet an start again, along with plumbing in a reverse camera and Bluetooth - then later I can see what's about and whether that can be incorporated