Check your state vehicle code, but my guess is that you will need them on anything registered as an RV. Further, the idea of spotlights which help light up the areas behind you when backing is a very good one, as shadows are NOT your friends. I also suggest that you consider the industrial truck style backup alarms. Remember that since your vehicle is moving, you are almost certain to be held responsible (liable) for any damage or injury resulting from backing up. Anything which makes it easier for you to see, and which does more to communicate to others that you are moving backwards, is your friend.
In Washington, as a result of a commercial truck running over a child in a backing accident, certain trucks are now required to have an additional mirror on the upper rear corner which can be seen from your regular mirrors - it shows the area in tight against the back of the vehicle. All are good ideas, especially when there are many areas of the world in which getting out of your vehicle is not a good idea.