Exercises at Desk

Is anyone doing any desk exercises? I got tired of sitting then tired of standing. Now I'm using a Twister Board much of the day, which has my calves looking great (not my abs so much as advertised though), but I want to work in some variety now.  I have looked at the ellipticals and bikes, but I'm concerned about the stride being long enough - I have that problem with cheap exercise equipment in general. 

The more I can do to break up the monotony of the day and combine work and movement the better. I need to move my arms more, too, but I haven't figured out how to do that without impacting the mouse/keyboard productivity.