Wearable trackers and mobile applications can facilitate self-reflection of doing physical activity. The gamification process incorporates game design elements with persuasive systems in order to encourage more physical activities. In this paper, the design of a mobile game, FitPet, is introduced. FitPet is a mobile application that combines ubiquity and simplicity of mobile devices with the engagement of computing games, intended to motivate people to incorporate more walking into their daily life routine.