We have built Drift, an application that measures and provides feedback on how far from the ideal path an orienteer has deviated, to study how sports apps can draw on real-time data to enrich sports activities. Orienteering is an outdoor navigation sport requiring mental skills and fast running through the terrain. Participants appropriated deviation into their practice and found new ways it could integrate with common orienteering practice. Interaction around deviation provided possibilities for new forms of sporting practice and social interactions. Deviation as a measure allowed this because it was highly specific and well-grounded in a specific skill of the sport. We believe this use of data in real time has the possibility of supporting and renewing sports activity as well as offering new opportunities for design.