I was wanting a footrest tonight and dh suggested using my stability ball.
I was the right height and I found I could do some simple leg and core movements while watching tv.
I don't have MS, but do get restless legs and maybe this will be a good thing to do each evening. I find if I do a certain level of activity during the day my legs don't act up at night.
Basically sit in your favorite chair/couch and prop feet/ankles on the ball and experiment - bounce, roll forward/backward, side to side and focus on slight core contractions to work out.