You can trust your smartphone app to track your physical activity says a new study. Although wearable devices have received significant attention for their ability to track an individual's physical activity most smartphone applications are just as accurate according to the study. In this study we wanted to address one of the challenges with using wearable devices: they must be accurate. After all if a device is going to be effective at monitoring -- and potentially changing -- behaviour individuals have to be able to trust the data said lead study author Meredith A. Case a medical student at the