Im looking at getting the unit 8100 but i would like to know how is the video bypass are we using a relay or a pin movement or no can do

Go to the root of the NEX forum and look at the very first pinned thread "Official AVIC NEX Bypass (AVIC Units Only). Two methods, software (easy) and electrical (via a pin movement). That thread shows it all.

I just grounded the wire and did the software method:

Step 1 ground parking brake wire

Step 2 turn power on push main menu button (bottom center)
Step 3 push AV icon (bottom center)
Step 4 on AV icon screen push off button (towards bottom)
Step 5 touch quadrant 4 (half inch in and half inch up from left lower corner of touch screen) hold your finger there for about 10-12 seconds. "set on" icon will appear that means you are done.

source: http://avic411.com/index.php?/topic/38589-official-avic-nex-bypass-avic-units-only/