Brickwood et al. 2019, Consumer wearable activity trackers, a meta-analysis

Systematic review and meta-analysis of consumer wearable activity trackers. Trackers significantly increased daily steps and moderate-to-vigorous activity, but at low-to-very-low certainty of evidence, and sedentary behaviour did not change. Multifaceted interventions (tracker plus coaching, goal-setting or support) produced effects approximately 44% larger for daily steps than a tracker used alone (685 vs 475 steps/day). Evidence certainty varied by outcome: low for daily steps, very low for MVPA and sedentary behaviour. Moderate.