A friend asked whether I'd ever used a Buja Board—typically a 3'x3' piece of plywood with half of a small-to-medium ball (like a jolly ball) attached underneath in the center--or all of a smaller ball, like a softball--so that the board rocks around in all directions. It's designed to allow you to play with your dog while getting him used to the idea of motion underneath, such as for eventually teeter-totter training, wiggly tables, and so on.
I've used one a few brief times. I have a table here that's just pretty wiggly to begin with, and for Boost I just put the top on the ground with random things under it to make it wigglier and to bounce from side to side kinda like a very low teeter. Neither she nor any of my dogs have ever been particularly bothered by things moving under them, so I haven't gone out of my way to pursue it beyond the occasional "here get on this wiggly thing." I put boost on the board that Lisa Maynard had in class for the puppies and, with our bit of background play in my yard with my table top, she barely even noticed that she wasn't on bare ground any more. I don't think it wiggled any more than my makeshift one did.