I was wondering if it is possible for the rear passengers to listen to their video through a headrest headphone output while you are listening to something else. Al and Eds installed head rests in my car that does not have headphone outputs so I am just wondering if they did, would they work or not. I will be replacing them with ones with a headphone output if this does work.

Yes It will work. I did it on my Z1. I have 2 HR monitors that have headphone jacks and the rear passengers can listen to movie audio over the headphones while I am listening to another source. You have to be sure that the video is not in mirror mode.