Well, it was a success! I might possibly have the first and only Infiniti JX35 that displays movies on the front Navigation Screen while the vehicle is in motion!
It was actually a very easy modification. I have now done this same mod on a Murano, two different Armadas, my G37, and now my JX35. Again, you tap into the VSS wire and the Parking Brake wires at the back of the AV unit. Using a DPDT switch that is $4 from Radio Shack and 3' of 4 wires I ran the wires from the back of the AV unit (VSS to AV unit, VSS away from AV unit, Parking Brake to AV unit, and Parking Brake away from AV unit. The DPDT switch flips everything from a normal working "stock position" to a position where the VSS and Parking brake "trick" the AV unit into thinking it is grounded (and it technically is) by running the #5 and #6 position of the DPDT switch to a ground. Actually the hardest part of the whole modification was finding a good and convenient ground. The center cluster pops apart quite easily, and there are only 8 screws that get removed along the way.
You start by removing the rubber tray near the 12v outlet, the next piece is the black plastic "tray" as it is referred to. This pulls straight out at you. Next piece is the lower cluster finisher, this has the nice finish (either Kasani Washani.....LOL, whatever it is called, or Maple Accent). This pieces also pulls straight out at you. You now have the HVAC control panel as the next piece. You will see 2 screws, remove the 2 screws and this also pulls straight out at you (unplug the wire connector). Next is to remove the piece that has the DVD/CD slot on it. First remove the 2 exposed screws. Again, this pulls straight out at you (again, there is a wire connector you need to remove). Finally, you will see a total of 4 screws that secure the bracket that holds the AV unit. Remove the 4 screws. You are now able to pull out the AV unit, the wiring harness we are tapping into will be at your top left. This harness has 16 pin locations across it, and it is 2 rows high. Unplug this harness, this is the harness you will be tapping into. I will post the diagram from the FSM that shows the exact pin location, but if you unplug the harness, and you look straight at the wires facing you, on the top row going from the left, the first wire is Green, this is the Parking Brake wire. On the bottom row, again, going from the left, the 4th wire in is a Tan/Brown Color, this is the Parking Brake wire.
That is the short and skinny of this, please post any questions, I will be happy to reply. Also, you can see a similar thread in Armada/QX56 Forum that explains this all in detail, same things apply, just make sure you are tapping into the correct VSS wire and the correct Parking Brake wire.
This is such a great mod on the JX, cool thing is you can display movies with your iPhone providing you have the cable to plug it into the AUX jacks in your center console. The screen is so nice and big in the front too, GREAT for movies!!!