A new application architecture is designed for continuous, real-time, distributed wireless sensor networks. We develop a wireless sensor network for machinery condition-based maintenance (CBM) using commercially available products, including a hardware platform, networking architecture, and medium access communication protocol. We outline the design requirements for wireless sensor network (WSN) systems specifically for CBM and thus take an application driven system design. We also investigate the physical layer of WSN by modeling the battery consumption of radio hardware used on the sensor nodes. We thus incorporate both application requirements and physical layer functionality in the design of our single-hop networking architecture, and User Configured Time Division Multiple Accessing (UCvi TDMA) MAC protocol. In our design, we emphasize energy efficiency and latency requirements posed by resource constrained WSN and our application domain respectively. We use modified RTS-CTS mechanisms for combining contention with scheduling to provide an overall energy efficient, scalable and adaptable MAC protocol with no collisions and minimal protocol overhead.