A Fitbit activity monitoring device can be used to measure how physically active your residents are, a new study suggests.

The company sold 21.4 million connected health and fitness devices in 2015, with 8.2 million  sold in the fourth quarter alone. But despite such growth, there has been scant research on how accurate they actually are. Researchers from the Charles Perkins Centre at the University of Sydney concluded that they are pretty close.

For the study, investigators examined four dozen patients and family members participating in community-based exercise programs. Participants wore the device over four days to monitor daily step counts and minutes of moderate to vigorous physical activity. The researchers discovered that:“Fitbit-Flex is a valid, reliable and inexpensive alternative device for activity monitoring specific to predicted attainment of physical activity guideline recommendations,” authors wrote.

These devices can give activity directors “real world assessments of their patients’ daily activity
patterns,” the authors said in the European Journal of Preventive

The Fitbit was introduced in 2008 in San Francisco by co-founders Eric Friedman and James Park. It’s essentially a 21st-century pedometer.

Throughout the day, Fitbit logs a range of data about the user’s activities, including the number of steps taken, distance covered and calories burned. n