The emergence of converged mobile devices with a wide range of computing, communications, entertainment, and sensing capabilities represents a major step in the evolution of wireless computing. Such devices increasingly shift the decision-making power from the user to the machine, which has the capacity to be better informed about the current environment and can respond more quickly. A trail is a collection of locations, together with associated information about these locations and a recommended order for visiting them. Mobile, context-aware trails-based applications range from single-user systems that focus on individual daily activities to multimedia groupware that supports a wide collection of user requirements. The trails metaphor makes it possible to explore adaptive characteristics common to all mobile, context-aware applications. Adaptation in this context involves altering the set of interest points on a trail and their visiting order with timeliness, accuracy, and relevance while remaining in tune with user expectations.