Maybe I am slow on the uptake but when I am preparing to reverse, I tend to engage reverse gear before I move. I also cannot see the advantage of watching my towbar and the ground around it while sat at the wheel. If I had an A frame or something on a towbar mounted rack, I might want to check it now and again while on the move.
If I wanted to use a camera as a rear view accessory I would fit a dual lens camera with one lens looking back down the road and switch it through a switch on the dash (I would not need a permanent live supply even then). My van is already set up with a Monitor that has an AV1 and AV2 input, it also has a spare wire running front to back in case it is required. I am quite happy with one camera pointing down that is only used when reversing. What anyone else has is down to them and of no concern to me, I stick to trying to answer the question asked by the OP. Threads on here tend to get taken off subject, possibly by people trying to be helpful but just confusing the OP even more. As my old Headmaster used to say, always read the question and then read it again.
