I found an old half medicine ball (not sure what it's called) laying around my parents house and I stand on it at my desk. It felt weird at first but I'm used to it now and it seems to keep my muscles working.I'm not sure exactly what it'll do to me in the long run though.
My thoughts to those who want to try it:
+ Give it time. The first 3 days were hard. After a week, it started to feel normal.
+ Get some padding. I'm using a cheap Yoga mat. I've heard gel mats are ideal.
+ Suck in that gut. If you practice keeping your lower stomach muscles tight when you start. This will help your back muscles learn to be straight.
+ Put both feet on the ground. Leaning on one leg isn't good.
+ Move around. Sway from side to side. Pick your feet up regularly. This helps keep your body and legs healthy.