This idea is similar to a stationary excercise bicycle, but with only the pedals. A small rectangular unit (appr. 12"x18") with bicycle pedals on either side is placed on the floor, under an office desk. The unit has variable resistance settings for a heavier/lighter workout.
The unit is simply placed under the desk and the person operates the pedals while working at his/her computer,etc.
This could help eliminate the very common, "Office-Butt Syndrome" caused by sitting at desk eating M&M's for eight hours per day.