Pervasive Computing environments range from basic mobile point of sale terminal systems, to rich Smart Spaces with many devices and sensors such as lapel microphones, audio and video sensor arrays and multiple interactive PDA acting as electronic brief cases, providing authentication, and user preference data to the environment. These systems present new challenges in distributed human-computer interfaces such as how to best use sensor streams, distribute interfaces across multiple devices, and dynamic network management as users come an go, and as devices are added or fail. The NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY SMART DATA FLOW system is a low overhead, high bandwidth transport mechanism for standardized multi-modal data streams. It is designed to allow integration of multiple sensors with distributed processing needed for the sense-recognize-respond cycle of multi modal user interfaces. Its core is a server/client architecture, allowing clients to produce or subscribe to data flows, and supporting steps toward scalable processing, distributing the computing requirements among many network connected computers and pervasive devices. This article introduces the communication broker and provides an example of an effective real time sensor fusion to track a speaker with a video camera using data captured from multi-channel microphone array.