To overcome situational hurdles when researching transformative learning in adults, we outline a research approach using single-case research designs and smartphone data collection apps. This approach allows researchers to better understand learners' current lived experiences and determine the effects of transformative learning interventions on demonstrable outcomes. We first discuss data collection apps and their features. We then describe how they can be integrated into single-case research designs to make causal inferences about a learning intervention's effects when limited by researcher access and learner retrospective reporting. Design controls for internal validity threats and visual and statistical data analysis are then discussed. Throughout, we highlight applications to transformative learning and conclude by discussing the approach's potential limitations.