 The study is a Randomized Controlled Trial RCT of a 12-week physical activity intervention. Fifty cancer survivors will be recruited and allocated to one of two research arms: FitbitOnly Group or FitbitCharity Incentives Group. Participants in both intervention arms will be asked to track their physical activities using Fitbit One, an activity monitor that monitors steps and physical activity and will receive basic educational materials about increasing physical activity. Those in the Fitbitcharity incentives Group will raise money for cancer charities if they meet weekly step targets. 