Two things have saved me countless times in business meetings: wiggling my toes and having a pencil in hand that I can twirl. I had to get an MRI AND a bone scan in the same day a couple of years ago. That was about 2 hours worth of having to stay utterly still. I pretended that my breathing was a see-saw and that I was playing on it--when I inhaled, the see-saw went up; when I exhaled it went down. I envisioned pushing off the ground with my feet and using them to bring me back down gently. It seemed to satisfy my fidget need because I was able to stay still.