The Future Mobility Survey (FMS) is a smartphone-based prompted-recall travel survey that aims to support data collection initiatives for transport-modeling purposes. This paper details the considerations that have gone into the survey's development, including the smartphone apps for iPhone and Android platforms, the online activity diary and user interface, and the background intelligence for processing collected data into activity locations and travel traces. The various trade-offs concerning user comprehension, resource use, and participant burden, including findings from usability tests and a pilot study, are discussed. Close attention should be paid to the simplicity of the user interaction, determinations of activity locations (such as the false positive and false negative trade-off in their automatic classification), and the clarity of interactions in the activity diary. The FMS system design and implementation provide pragmatic, useful insights into the development of similar platforms and approaches for travel and activity surveys.