I wonder if an option to keep your body moving (similar to Ben's standing pad) while sitting at a computer for long periods of time (if this is due to work, study, etc.) would be to sit on one of those big gym balls instead of a chair? (wellnessmama.com)
Athlete is on their front over a table of gym ball and raises the arms back while squeezing the scapulae or shoulder blades (sportsinjuryclinic.net)