That sounds like it would work to me....as long as yo udon't wanna wathc them while the car is moving....or have anyone else watch them while riding with you. As for the grounds....I'm not sure there. I've never shared grounds with anything. If you can use seperate grounds for each screen and the HU...try it, but if you have to use the parking brake for safety reasons...and legal ones too....I can't think of how to do that.