The e-brake wire needs to be tapped to keep you legal - it's illegal to have a movie screen visible to the driver while the vehicle is in motion. I've seen people stopped for driving around while watching television.

But your life is your life - just don't hit me or mine! I try not to invite the police into my life.

Some of the GPS/DVD players are smart enough to detect the bypass with the wire grounded. Some will detect that the wire has been grounded for too long and others will sense the car's motion (like the Pioneer AVIC's) and such the video off. The way to bypass the first is to use a toggle switch or relay. The Pioneer's can be defeated with a modification to the circuit board.