A study from vpnMentor dives into the data collected by wearable devices, such as smartwatches or EEG headbands, to better understand how the collected data is being used. 

The research found that 90% of devices collect health and wellness data, making it the most commonly tracked category. 71% track heartrate, 56% assess blood oxygen, and 29% monitor skin temperature variation. Similarly, 87% track fitness and activity data, and 83% analyzed sleep information. 

Location was tracked by 63% of examined devices. 49 devices were shown to utilize GPS tracking, and 28 depended on a smartphone for GPS tracking. 

The research found that out of 33 notable brands analyzed, 7 explicitly sell or share collected data to third-party advertisers or marketing partners (23%). In total, more than half (55%) of all analyzed brands were found to share de-identified biometric data with outside researchers.