I added a $70 wired camera to my 33' TT last year. For the price, it does the job but the screen resolution isn't the clearest. I initially mounted the camera to a bracket above the spare tire but excessive vibration on the road made it impossible to get a clear image. Mounting the camera directly to the bumper solved the vibration issue but the focal length on the camera is pretty short so I don't see cars 4-5 car lengths back well...they are just a blob on the screen.
For highway observation, my set up is adequate but I don't rely on it as a back camera. I don't have any perspective on where the left and right edges of the trailer and there's no sound so the DW still backs me in when kids are present at the CG.