I did the OEM Invision headrest monitors. They come already factory matched, extremely easy to install. I actually installed the headrests myself and then had a buddy of mine supply the ground and power to the "brain" of them. It's a pretty neat setup, totally exclusive of the existing rear entertainment setup.
You can put a DVD in one headrest and "sync" it over to the other so both kids can watch the same thing, or watch independent shows on each monitor. They came with infared wireless headphones and even my 3 year old wears them without issues.
The TVS can be tilted down if need be for better viewing, you can supply your own video source too. We plug in our iphones into the TVs and stream Netflix directly to the monitors. Works pretty well!
I can get the OEM ones if you are interested. They are 7" monitors. They aren't exactly cheap, but the fact that they are factory headrests that just swap out with the existing ones is pretty nifty. All 100% plug and play.
