A Wireless sensor network (WSN) consists of a potentially large number of sensor nodes with wireless-communication capabilities that work collaboratively to achieve a common goal. While every WSN application has specific requirements, there are some common basic services that any WSN must offer in order to support applications. There are available commercial WSN nodes offering such basic services, but they are still very expensive. So, we ask ourselves if it is possible to build a WSN node keeping low costs, while at the same time implementing these basic services: the answer is yes. We built sensor nodes and we call them WiSe-Nodes. In this paper we present the architecture of our WiSe-Nodes as well as the details about their hardware modules. We present also an hybrid MAC-routing protocol called WASP that implements the basic services of a WSN. Finally, as a tool for the WSN developers we introduce our simulator YAWSS that provides a controlled test environment where new WSN protocols can be tested and executed before implementing them in hardware.