14-18 years old

lives in the Seattle-metro area

able to complete forms in English

no restrictions by a health care provider on physical activity or walking

own a smart phone or similar FitBit compatible mobile device (e.g. iPod Touch)

agree to install and share data from the FitBit Flex smart phone app with the investigators

attends study high school or health clinic or receives and clicks on a Facebook advertisement for the study

A Wearable mHealth Device to Promote Teenagers' Physical Activity