I've got everything working properly, using my Fatsharks...but let's say that someone(s) is with me and they'd like to see what I see. I'd like to buy a viewing monitor for the other spectator(s). How would I hook this up to the mix?
There should be a 1/8" video Input/output connection on the right side of the goggles, next to the power input connector. It will feed an RCA video input to an external device. Try it with your home TV set while indoors testing.
You could also get a cheap second receiver on the same frequency and hook that to your second device.
That way you are not tied to the screen with a cable, although if you are using an external receiver that's not really and issue.
I will vouch for there being latency on that output of the goggles. I drove my 4x4 by watching the TV, but is was noticeably out of sync with reality. I will now be considering a second receiver too.