Digital technologies play an important role in our daily lives. Smartphones and tablet computers are very common worldwide and are available for everybody from a very early age. This trend offers the opportunity to track digital usage data for psychological and educational research purposes. The current paper introduces two research projects, the "PhoneStudy" and "Learning4Kids" that both use mobile sensing software to collect ecologically valid data on the usage of applications installed on smartphones and tablets. This usage data is used for statistical analyses, for a reward system, and to provide feedback to the study participants. The advantages and challenges of using mobile sensing compared to conventional forms of assessments, and the potential applications of mobile sensing in psychological and educational research are discussed.