That's quite impressive, very well done - if you are able to hook that into your OBD port you can have on-the-fly vehicle information too, which is quite spectacular!
I think you might benefit from a roof console, because your radio mike isn't going to be easy to get to.
If you're going to make it play video streams, remember that the unit is not supposed to be able to do that for the driver, only the auxiliary screens, while the handbrake is not in use (use the handbrake switch to turn the safety feature on and off). I think there might even be a law in relation to it, I know my in-dash unit is incapable of playing video streams to the main screen while the handbrake is off.
Awesome job!