upgrade your 6.5"screen to 7"
 

When I was checking Audi video in motion, I noticed an interesting unit on this website car pad for Audi NewA4L,Q5,A5,AUdI DVD Player
NEW GPS & reverse cam for A4, A5, A6, Q5, Q7
7" 800x480 screen replace the 6.5" screen , you'll get touch sreen navigation and gps + much more: It does have video in/out+rear camera input with dynamic guidelines.
So I bought 1 set to installed in my Audi A4,Device was really easy to install. It took about 2 hours from me.
Here is the link of finished install the device of my car,share with you.
Video - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting
developed as a direct SCREW-IN REPLACEMENT for your existing low resolution (400x240) 6.5 inch LCD display. This is also available for A6 and Q7 owners, as well as ALL A4, A5, and Q5 models (including those with MMI).It offers the following features:
*Sharp, clear, HIGH RESOLUTION 800x480 display (configurable for brightness, colour).
*Direct touch-screen operation.
*All existing car "infotainment" and MMI functions remain totally unaffected.
*GPS operates in background mode whenever the screen is powered, giving fast startup when selected.
*Option of standard 6.5 inch mode or INCREASE TO 7 INCH if you want.
*All functions built in to screen unit, no "box" in the glove box or anywhere else.
*Newer Windows CE 6.0 core allowing more choice of software.
*Simple plug and play installation, this is REALLY EASY to put in.
*Excellent reversing camera image (high res).
*Reversing camera image includes DYNAMIC PARKING LINES that curve with your steering (like factory system), and outline image of vehicle showing rear parking sensor action if installed.
*Separate independent speaker for GPS voice leaving your sound system untouched
*AV functions - two AV inputs allowing dvd or ipod/smartphone inputs; two video outputs for rear seat screens, audio output to infotainment (AMI or AUX).This makes it really easy to get GPS and reversing camera for your car.A replacement high resolution screen with all the goodies built in!If you touch the screen, these two discrete "buttons" appear on the screen, allowing you to select the GPS menu:

There is no extra charge for the 7 inch screen because THEY ARE ALL 7 INCH! There is a setting in the config menu to select 6.5 inch mode (image shrinks a little from the edges) or 7 inch mode (full screen).When you get yours it will be set for your car's actual requirements, but you can change it in the future...

After much research I have found, installed, and tested an aftermarket GPS solution that is integrated with the genuine LCD screen in the centre dash of these vehicles. It includes a reversing camera connection and a number of other functions. The GPS runs IGO8, OZI Explorer and most other WINCE nav software.