I have used this system on the last 2 motorhomes we have owned. I thought it was a good idea and I am going to share it with you all.
All modern back-up camera systems are equiped with one way audio to the cockpit of the motorhome allowing one way communications. When I purchased a CB for the motorhome it had to have a PA (public address) function on the radio. I ran a speaker wire from the pa port on the rear of the radio to the rear of the motorhome and installed an external feed horn type speaker near the trailer hitch and now I can talk to the person who is guiding me into a space or whatever. I find it very useful!!