Impressive results, but I think it is important to keep in mind that most of the examined studies in this meta-analysis combined wearable activity trackers with an intervention. The effect of only using a wearable is probably much smaller and the duration of the effect is unclear.

From the limitations section of the discussion:

“Although this umbrella review provides strong assurance of the efficacy of wearable activity trackers in increasing physical activity, few of the systematic reviews and meta-analyses examined the effectiveness of wearable activity trackers alone. […] the multifaceted interventions yielded effects around 50% larger than those using wearable activity trackers alone.”