Studies show that 14-to-40 year olds are spending more time at the computer and less time exercising. Using Contextual Design, our group tackled the challenge of motivating people in that demographic group to exercise more. The result is the "PEDdo" (Latin ped: foot, Persian do: two) ? a device which encourages physical activity of its users in an entertaining way and reinforces positive exercise habits. Keywords Exercise, Obesity, Physical Activity, Contextual Design, User Motivation ACM Classification Keywords H.5.2 [User Interfaces]: Graphical user interfaces (GUI), Prototyping, User-centered design