I'm looking to replace my top screen with some kind of touchscreen with built in functionality. This is what i mainly want:

1. apps on my screen, such as Waze, music, etc.
2. attach rear view camera. i dont have one, so would like it to support one
3. still retain my lower head dash unit items and functionality
4. still retain all the other items in my screen

I know Android Auto is coming out, and would love that. I would like to only replace the top screen. I'm not sure how great the aftermarket items are, but something like this would be great. if it allowed me to install apps as well.

Car Media Center Player for Audi A5 A4 Q5?2008 2009 GPS Navigation Stereo | eBay