Cubicle Dweller / Remembering to Stretch

Does anyone know of a utility that reminds a computer user to get up and stretch every once in a while? Perhaps something that pops up a specific stretch to do?

The BC Worker’s Compensation Board has a free utility for this, as long as you don’t mind the prompts being given by an animated puppet:
http://www2.worksafebc.com/Topics/Ergonomics/Re…

I’m all for animated puppets, thanks Diane!