Recent advances in wireless communication and sensor technologies have opened up a new paradigm in healthcare industry. More and more attentions in the wireless body area network (WBAN) have been received recently. However, the limited network resources constrain the application development in WBAN. In this paper, we present a service-specific middleware architecture to bridge the gap between the application development and the underlying network sensor devices. The proposed middleware is able to provide functions including network initialization and registration, service announcement, sensor actuation and control for flexible multiple modalities data acquisition, and real-time network service management. The middleware has been implemented and tested with a healthcare monitoring test-bed using Imperial College sensor nodes.