I use this system. It leverages the WVCMS130AP auto-paring wireless camera which is really slick. I bought a 2nd camera and use one on my other car-hauler enclosed trailer. I only use one camera at a time (obviously) and since they're auto-pairing it's easy to switch between them, you just pair with the one on the trailer you're towing at the given time.
As for range, I had the RV one installed on my old 32' Travel Trailer and the unit had sufficient signal strength out the box and worked great. When I moved up to my current 38' fifth wheel, the unit is at the very end of it's effective range. Still able to use as a backup camera, but going down the road and the signal will drop out frequently.
I bought an
antenna extension kit for the WVCMS130AP camera and was bringing myself to the daunting task of running the extension half way up the coach. Then I noticed the extension kit comes with a long(er) high gain antenna then that of the original one on the camera. So on a whim I simply removed the original and screwed on the longer one and wha'lla it now has enough signal strength that I don't have to run the extension wire. I suspect that if your rig is over 40' that you'll need the full extension in order to maintain enough signal strength to be useful.
As for overall camera performance, it works pretty damn well. I like the fact that you can turn-up the audio and hear what's behind (in addition to see). A couple drawbacks are; if you wire off the indicator lights (easiest) then you're forced to keep those running in order for the camera to operate, and the unit doesn't have any sort of scale or visual bars that can overlay on the image which is useful for backup purposes (like a typical backup camera would).
Otherwise I'm happy with the purchase and would buy again if I had it to do all over.