Digital activity trackers are becoming increasingly more widespread and affordable, providing new opportunities to support participatory e-health programs in which participants take an active role. However, there is limited knowledge of how to deploy these activity trackers within these programs. In response, we conducted a 7-month study with 212 employees using a wireless activity tracker to log step count. Our results suggest that these devices can support improving physical activity levels and consequently reduce diabetes risk factors. Furthermore, the intervention seems more effective for people with higher risk factors. With our work we aim to contribute to a better understanding of the issues and challenges involved in the design of participatory e-health programs that include activity trackers.