Our research, part of a larger study on exercise and well-being, focuses on the use of interactive artefacts in public spaces. Our findings suggest that many people have concerns about exercising in public due to inhibitions, insecurities, and social anxiety, which can affect behaviour in this context. Both well-being and physical mobility—the desired outcome—can be improved by new opportunities for activity, especially after the COVID-19 pandemic. The implementation of technological innovations, especially interactive ones, seems to be promising when it comes to encouraging active lifestyles and mobility in public places. Through its exploration of physical activity, this research unveils the social aspects inherent in the use of interactive projection in urban public spaces. We took an “in-the-wild” approach and conducted public studies using a research through design methodology. We found that while interactive projections can stimulate physical activity, effectiveness and acceptance are significantly influenced by interpersonal behaviours. Thus, changes in social interactions among different stakeholder groups could be observed both inside and outside the interaction space. This work highlights the need for future studies to consider visible and invisible social dynamics in the design and use of interactive public systems.