i also installed the dvd in motion on my car... however instead of installing monitors i got me some ipad minis for a little over the monitors price and those things can go with me anywhere... also i only got me the wifi only since i have wifi integrated to my car... netflix or any other video source works fine for my kids.... i do not remember the wifi router. model but i will look it up and post here i got it at Tmobile with unlimited data for 15$ a month.
the other reason to why i went with ipads is that when i decide on selling the car those things will stay with me... the ipads and holders stay.
for audio i use a bluetooth dongle to stream to my head unit from htc..
and if i do not want to hear the ipads they use a pair of jabra bluetooth headphones. i got them for 20$ a pair on amazon.