The advent of mobile smartphones and similar technology has opened new opportunities for studying human mobility within psychology and companion disciplines such as human geography, demography, and sociology. This article examines how such research raises novel ethical concerns. To do so, we outline two research projects: one based in Northern Ireland (The Belfast Mobility Project) and the other in Chile (The Norm-Contact Mobility Project), drawing concrete examples of the ethical challenges encountered throughout both projects, which used global navigational satellite systems as a tool for data collection. We discuss new threats to participant confidentiality and anonymity, problems of “unanticipated” data collection and exploitation, emerging difficulties in achieving properly informed consent, and concerns regarding the representation of vulnerable populations with limited access to smartphones and a legitimate fear of surveillance. We also reflect on the different measures we took to tackle these challenges and discuss the importance of implementing wider changes in the protocols associated with basic ethical research principles.