Mike,
don't know yet if DVD will play video on NAV. So far, what is clear about the video on NAV is:

Using the VAIS SL2Vi and video ipod
-the video plays very well on the NAV screen when parked if you ground the parking brake sensor pin (that does not even have a wire going to it in TCH 2007)
-when the car starts in motion, the video stops, though the sound continues
-if you cut the speed sensor wire and bring it to a switch so one side is factory default (speed sensor wire as is originally) and the other side of the switch the wire is cut, then when you "cut the wire" by flipping the switch the video stays on while in motion for about half a minute then stops. If you flip the switch to factory default and wait a minute then flip again, you can get another half min of video before it stops. So the NAV is smart enough (or has other sensor wires) to detect that parking break=ON and speed=0 while car is moving is a hack and the video stops after half a min.

What I suspect is possible but don't know how to do it yet is
-get the ipod video to play while moving
-get a video switcher that allows headrest DVDs to play on NAV
Questions for these issues are
-what has to be bypassed?
-and for the video switcher, does the DVD output have to be adapted in some way for the RGB of the NAV screen
If anyone had figured these items out, please post a comment.
Joe

Camry Hybrid 2007.
Mods: Backup camera. DVD/LCDs in headrests. VAIS SL2Vi w/video ipod. cellphone booster via roof antenna. Mobile WiFi via roof antenna. Scanguage II. 2 meter band ham radio via trunk lip antenna. Scanner via trunk mounted antenna. Valentine 1 hidden display.