Current research on context information focuses on the use of new kinds of sensors and on the aggregation and interpretation of sensor data. Having a closer look at applications supporting emergency scenarios with context information several problems arise. Emergency activities are complex coordination tasks which involve a multitude of different roles and resources. The definition of emergency scenarios and the mapping of relevant context information is a time-consuming and error-prone task. This work discusses how a model-based approach can support the definition of emergency scenarios at an abstract level. The abstract representation (PIM, Platform Independent Model) of an activity is then transformed into a platform-specific model (PSM), which includes a collection of context sensors. We show that the use of a model-based approach simplifies the definition of complex context-sensitive applications, and how this increases the flexibility to use different sensor platforms in different emergency scenarios.