What it is and the problem it solves
Fitbit is a line of wireless-enabled wearable fitness trackers introduced in 2009. It solves the problem of passive, continuous personal activity logging without manual entry.
How it works
Fitbit activity trackers sync to mobile phones or computers via Bluetooth.
What works
Hip-worn Fitbit devices measure steps within 1 step of 100% accuracy and underestimate calories by only 6%. The Fitbit Charge 2 accurately measures average heart rate during sleep in healthy adults. Sleep-staging models outperform non-sleep-staging ones at differentiating wake from sleep.
What does not
Wrist-worn Fitbit devices overestimate calories burned by 21% and miscount steps by 11 per minute. They overestimate sleep efficiency by 4% relative to EEG. The Fitbit Force was recalled in 2014 due to allergic reactions.
What it changes
It changes how individuals self-monitor movement and sleep—but not clinical measurement, forensic evidence, or health outcomes. Its use in criminal investigations relies on timestamped activity logs, not diagnostic-grade data.
Is it worth your time
It is worth your time only if you need a low-cost, Bluetooth-synced wearable with peer-validated accuracy for step count and heart rate—but only when worn on the hip or used for sleep staging, not for calorie estimation or wrist-based precision.
