Providing navigation assistance to users is a complex task generally consisting of two phases: planning a tour (phase one) and supporting the user during the tour (phase two). In the first phase, users interface to databases via constrained or natural language interaction to acquire prior knowledge such as bus schedules etc. In the second phase, often unexpected external events, such as delays or accidents, happen, user preferences change, or new needs arise. This requires machine intelligence to support users in the navigation real-time task, update information and trip replanning. To provide assistance in phase two, a navigation system must monitor external events, detect anomalies of the current situation compared to the plan built in the first phase, and provide assistance when the plan has become unfeasible. In this paper we present a prototypical mobile speech-controlled navigation system that provides assistance in both phases. The system was designed based on implications from an analysis of real user assistance needs investigated in a diary study that underlines the vital importance of assistance in phase two.