Modern multimedia applications use an increasing number of sensors including cameras, microphones and microphone arrays. These applications must acquire and process data from sensors in real-time, which is usually beyond the capabilities of single machines. We present our distributed sensor data transport middleware, the NIST data flow system II, which offers network transparent services for data acquisition and processing across a local network of computers. An application is thus represented as a data flow graph, with streaming media flowing between the different computational components. This is highlighted by presenting a multimedia application tracking persons using a sensor fusion of audio and video streams.