We present the design and implementation of a unified ac-cess platform to sensor networks based upon Web Services. This allows other systems in heterogeneous environments to easily consume and process sensor network data transmitted by sensor nodes. Clients can subscribe to different node or value types while data filtering is performed on the server side. The system design is modular and all components are exchangeable. The prototype version uses ZigBee as an ex-ample wireless communication technology. To demonstrate the capabilities of the system, four different clients were de-veloped that demonstrate different access strategies in ho-mogeneous and heterogeneous environments.