We did a cross-country journey using a laptop to play DVDs. Plugged in the sound to the car system. Passenger could watch and listen, driver could listen in good fidelity. It was an OK experience, but for the most part we preferred to look at the scenery and converse.
Seems to me one of my earlier Mustangs allowed DVD movies to play when the car was stationary, prohibited them when moving (or engine running?).