Modern Wireless Sensor Networks offer an easy, lowcost and reliable alternative to the back-end for monitoring and controlling large geographical areas like Buildings and Industries. We present the design and implementation details of an open and efficient Prototype System as a solution for low-cost BMS that comprises of heterogeneous, small-factor wireless devices. Placing that in the context of Internet of Things we come up with a solution that can cooperate with other systems installed on the same site to lower power consumption and costs as well as benefit humans that use its services in an transparent way. We evaluate and assess key aspects of the performance of our prototype. Our findings indicate specific approaches to reduce the operation costs and allow the development of open applications.