OP here -- so I looked into buying the walkie talkies, just out of curiosity. According to the reviews, they work well BUT they run through batteries very quickly -- these are the little AAA batteries. So just when you really need them to work, they don't.
I think I am going to stay with the hand signals. DW's signals are much like the ones described by Pangea Ron. The only difference is that the amplitude of the signals will vary. If she wants me to move the back of the trailer far to one side, she will point vigorously. If just a little motion is needed, the pointing is more limited. It works perfectly, as long as I can see her in the mirrors. (That's the minor problem, right there.)
