We define sensor middleware as the binding code mainly running between the sensor OS and applications g programming abstractions to bridge the gap between application developers and low-level hardware. Hence it serves the purpose of simplified integration of components developed by multiple technology vendors. Middleware for distributed systems is a relatively mature research area with a considerable amount of work done on the aforementioned topics. In this paper we explain why standard distributed systems middleware solutions are not suitable to address Wireless Sensor Network (WSN) problems. Illustrated by a health monitoring use case, we propose an enhanced middleware framework that better addresses the needs of WSN applications. Keywords- Sensor Networks, Middleware, Security