Excellent question! It may be a bit early to answer the question. We've had a camera installed and tested, but we haven't hit the road with it yet for more than a short test drive.
We ended up going with this camera:
Voyager Digital Wireless 7" Color Backup Camera System
RVCams Backup Cameras and Rear View Systems: Voyager Digital Wireless 7" Color Backup Camera System
The system has a single wireless camera and an LCD screen for your truck. The wireless camera still needs power but that's usually a matter of tapping into the 12V from nearby running lights. This YouTube video shows the general installation.
How To Install an RV Back-up Camera by RV Education 101® - YouTube
The system has support for two additional WIRED (not wireless) side cameras. I haven't ordered these yet but the rep at rvcams.com mentioned that I could add them later. I'm planning to have a cable installer run some network cable for me and will have him/her also install the wiring for these additional cameras too. A wired connection also means I'll need to order a wiring harness for the cameras so I can connect/disconnect them like I do with the trailer wiring harness.
The big question is how good will the reception be. On my first test, I had the camera sitting next to my cup holders and it held the signal during the test drive except it seemed to drop out once. The good news is that when it dropped the signal it was only for a moment and it didn't cause static or anything -- it just froze the image for a second. I expect that the reception will be better once it's mounted on my dash. (For reference I have a GMC Sierra 3500 HD Extended Cab Full Bed towing a 2013 Columbus Palomino 320RS 37' fifth wheel trailer)
One more thing I want to add is that while it doesn't need to be wired into your tow vehicle, mine came with a bunch of wires and I had to figure out which two to connect to the provided 12V adapter plug. These connectors just slide together but you'll have to identify which ones to connect. And for aesthetics, I gathered the rest of the loose cables together and wrapped them up with electrical tape.