Romeo et al. 2019, Can smartphone apps increase physical activity, a meta-analysis

Systematic review and meta-analysis of randomised trials of smartphone apps for physical activity. Pooled across six trials (1,178 participants), apps produced a small and statistically non-significant increase in daily steps (about 477 steps/day, P=.19). The effect was larger in the first three months and dwindled thereafter, the typical novelty-decay pattern. Moderate.