Recording HD video and displaying a live HD feed on a nearby screen are at different ends of the complexity spectrum. As GRJ posted earlier, there are plenty of compact devices that do a great job of recording an HD video to an SD card for an affordable price.
Broadcasting a "reliable" full frame HD image will prove to be a more expensive venture. Lionel's new theater care will do about 20 FPS with an excellent Wi-Fi signal. That FPS drops off quickly as the signal drops and minor freeze frames with image blemishes also occur. Generally, the car works perfectly within 30 feet of the device that receives the signal.
Also as mentioned above, broadcasting that to a large TV also becomes a hurdle. HD broadcasts take considerable data bandwidth, and for an iPad to receive one HD broadcast and then re-transmit it to another HD display would probable produce less than desirable results. Lionel also has software that can be installed on a PC which would be the better way to rebroadcast for their camera to a large TV display.
I have a scratch built wireless FPV analog camera car that I built using widely available drone equipment: https://ogrforum.ogaugerr.com/...35#72805549098596735
I have also tried many of the cheapo wifi backup camera systems that are used as and add for your car with mediocre results. The Wi-Fi video broadcast abilities of the go-pro is also underwhelming.
When it comes to live HD broadcast on a TV it boils down to these three features, but you can only pick two:
1) Great Frames per second (FPS) with low latency
2) Reliable & easy to use / setup
3) Affordable
