I have one that I got set up in the middle marker light.
I setup the monitor on the left hand side of my dash and have a power switch to turn it on or off as I please. I did not want it setup via my nav system because I wanted to keep the fuctions separate. I will be installing in the next month or so a new Pioneer Nav system, two headrest DVD players, visor monitor for the passenger side, detachable roof mount camera along with 500gig hard drive(to record off road adventures) and a 20" flip down monitor for the rear. The purpose of the rear 20" is so that when I play a movie we can all watch I can use the vehicles sound system to play it through and the kids will be able to view it from the rear. Hmmmm that will be a total of 6 monitors in the truck...time for a second battery!.
Cheers.