heavy exersise ball (not weighted but can stand on it) is should't be pumped all the way the less air easyer to stand on. use a frined to stand on it or put it inback or side of couch but dont let ball tuch it.
work on standing on the ball for a while then slowly work in squats then when u master than u can incorperate weights. its surfing training for balance in big waves. i saw laird hamilton doing this on fit.tv and been working on it (im doing no weighted squates now with a almost fully pumped ball)
when i wrestle back yard style video jiu jitsu (bought ceaser gracie video =) ) i found my stand up take down defense is better my legs are alot more strong and are harder to manipulate. they are used to the shakes and wabbles