Purple1,
We tried that a couple years ago and got absolutely no reception in our truck for the monitor. Called the company and they said it really doesn't get reception past 15'. Put it on the end of our 24" enclosed trailer and you can imagine our results.
73challenger,
We checked into that one as well but since we will be changing out what trucks will tow the trailer (dads and my truck) we wanted a set up where we could just plug in the monitor into the truck we decided to use and plug into the trailer harness or secondary harness for the camera system on the trailer.