Wearable devices incorporating actigraphic technologies are transforming the way researchers aggregate, display and interpret health-related data. These devices, and the mobile software applications built to work with them, enable researchers to monitor and capture data on a wide range of physiological functions. Andrew Kuhlman, Michael Murphy and Melissa L. Vadnais at Worldwide Clinical Trials look at the evolution of wearable technologies and how it influences the emerging use of actigraphy as an outcome measure.