I have one of Marc Parnes' balancer rigs as shown in the first post and it's a very nice piece. The single sided swingarm bikes require a specific variation of his balancer, as one of the cones is designed with a different diameter/angle for the rear wheel.
Very handy stuff, good not only for balancing, but also for checking out-of-round in the event of a spill, or for truing/lacing spoked wheels if you ride dirt, etc.