I just carry 2 orange cones on board.
I set 2 cones out on the CG site or anywhere where I want to be parked.
One on left side and one right and set them both how far back I need to back in. Easy peasy!
Shoot the MH between the cones and stop when the rear of your MH is even with the cones. Using both of the plain ole side mirrors your RV came with.
No DW's wavying hands yelling, no camera, no walkie talkies which still includes waving and yelling.
Nothing but silence when I back in AND nail it every single time. :C