Wearable sensor technology allows for monitoring movement in an individual’s native environment. These sensors are becoming increasingly widespread and low-cost; they already exist in many devices used daily by millions of individuals, such as cell phones and body-worn activity monitors. We are leveraging this exceptional technology to modernize health monitoring in the elderly and other patient populations and to provide on-field performance assessment for elite athletes. Our work in health monitoring includes developing algorithms to monitor elderly individuals and alert caregivers of a fall or other medical need. In sport, we are seeking to characterize underlying biomechanical indices that drive an athlete’s overarching performance strategy on the field. We additionally are identifying movement characteristics that govern performance degradation over time, such as what occurs in the presence of neuromuscular fatigue. This knowledge will in turn be used to develop powerful on-field tools for performance evaluation, training enhancements, injury screening, and return-to-play assessment for a variety of athletes and sport disciplines.