Available on Thingiverse
Create a cheap rear entertainment system for your kids.
I have used for mine 2 old Amazon Fire 7" tablets. Those stay charged up using the USB plug in the back of the seat.
I don't have a mobile plan in the car so the kids download some shows (netflix, disney+) from the house wifi.

 

That's awesome, thank you! I've been planning on making this myself but been procrastinating for months. Just in time for a long roadtrip with the kids.