I recently read a "systematic review" somewhat like this, on smartphone applications for precision agriculture. The authors did conduct databases searches for articles about smartphone apps, but they also directly searched Google Play and Apple App Store sites for apps with high user ratings. Here is the citation:
Mendes, J., Pinho, T., dos Santos, F., Sousa, J., & Peres, E. (2020). Smartphone Applications Targeting Precision Agriculture Practices-A Systematic Review. AGRONOMY-BASEL, 6.