When we had our 1984 Southwind we purchased and installed this wireless backup cam system off ebay from China for around $100. We used it with the monitor it came with for a couple years without any problems and it ran all the time since we used it as a rearview to keep an eye on our towed Jeep. I powered the rear transmitter and camera using the clearance/tail light circuit instead of running a new dedicated power source. When we sold that RV, I kept the system because it had worked so well.
Flash forward about a year and we've gone from a 27 footer to a 40 footer with zero rear visibility. We had planned ahead and already installed the new Kenwood DDX 370 for it's upgradeability so fitting in our old cam system was a snap.
I mounted the cam right below the center clearance light and drilled for the wires, ran them through and siliconed around them for a good seal. The small transmitter and camera were then connected into the clearance light harness for 12V supply. Done in the rear!
Next it was time to power and connect the cam receiver into the back of the Kenwood head unit. I powered the cam receiver via the same switch that turns on the clearance lights, plugged in the yellow video cable to the "reverse" input on the back of the Kenwood and then went into the head units setup menu to change the protocol to manual reverse cam button control. Now I can be listening to music and still keep an eye out back on our Towed.
We didn't end up using our old 7" monitor for this install but I'm sure we'll use it for something. Again, I am a passionate American and I wear American made boots but I can only afford to do so because I buy my electronics intelligently from the most affordable source. Don't get stuck on stupid.