In Reply In our Research Letter, we reported a study evaluating the accuracy of a convenience sample of top-selling smartphone applications and wearable devices for tracking physical activity data. We found that most devices were accurate for tracking step counts and that smartphone applications had less variability than wearable devices.
Even though only 1% to 2% of US adults own a wearable device, these technologies are receiving much attention for their role in tracking health behaviors and their adoption is expected to grow.1 The reach of smartphones is also increasing rapidly and ownership has increased from 48.2% of US adults in 2011 to 71.0% in 2013.2
Case MA, Volpp KG, Patel MS. Electronic Devices and Applications to Track Physical Activity—Reply. JAMA. 2015;313(20):2080. doi:10.1001/jama.2015.3880