We describe a framework for wireless sensor network (WSN) based mobile mashup applications. The framework consists of four functional components: WSN, mobile gateway, context management platform, and mashup server. The WSN deployed in the application domain senses the physical phenomena and the human-environment interaction and expresses them in sensor readings. The mobile phone is used as the gateway to the WSN, which can directly communicate with the sensor nodes and collect the user related sensor data. On the mobile phone, the raw sensor data is preprocessed and the user-centric contexts are extracted. The context management platform stores all contexts according to the predefined context ontology, detects the inconsistent information, deduces the high level knowledge using heuristic rules and provides web service application programming interfaces (APIs) to mashup server. The mashup server integrates the context information obtained from the context management platform with the information from other mashup data sources, and provides services to users through mobile phone. The proposed framework can be used in exhibition center, shopping mall, smart office/home, and many other scenarios.