I have the Voxx system installed. The first week didn't go well, each time we played a video the system would shut down after about 30 seconds. I took it back to the installer as they needed to swap the two screens (they originally put the master with the DVD player on the passenger side). They attempted to troubleshoot my issue but it operated perfectly for them (go figure). Since then it as worked great for me but I've only used it a few times since. I think it will take some more time before I can give a good review of it. Other than my issue with it powering off, all other functionality seems to be working good. I can mirror the screens with an app on my phone and fully control them from the front seat. Its not perfect by any means, but does work. You can't give the two screens a name so you have to remember the ip address of each to know which one you are controlling from the app, and to switch between them you have to close the app and re-open it, which is a little annoying. They are still running Android 8 which as long as they work I guess is fine, but I worry if apps will stop working on them some day. It appears I can install any app from the Google Play store, including games, maps, and of course the standard streaming apps. They seem to be quick responding. You can mirror the slave to the master so that they both display the same content, and they have built in FM transmitters so the audio can be heard through the car speakers. This can be a little staticky but perhaps I need to try a different frequency. For kids in car seats, I wish the were mounted a little higher behind the headrests, the middle of the screen sits where the head-rest and top of the seat meet, making it too easy for a kid in a car seat to kick. I wish they were higher like the factory screens which are directly behind the headrests. Also, you have to power them on by pressing a power button on the screen, you cannot power them on from the app.
They are expensive, I paid $1900 installed. The only reason I decided to give them a try was that I wanted to be able to control them from the front seat. If you don't need that functionality, I would simply mount a i-pad or tablet to the headrest which think you could do for about half the cost.
Other benefits are that I have fully functional pads with touch screens, no remotes, and no wires. With a factory setup using an external device I wouldn't have been able to control them from the front seat, so I am still hopeful that long term I will like them.
I'll report more later after I use them a little more.