We present the most significant issues found during the implementation of IEEE 802.15.4-based communications in a set of wireless sensor nodes developed for ambulatory biomedical signal monitoring. The technical specifications of the Personal Area Network Coordinator and these of a body temperature sensor node are described. Topics regarding to network functioning like topology, device roles, medium access, packet transfer and nodes programming, are tackled based on the requirements to be fulfilled in order to provide a monitoring instrument to conduct experiments which could provide useful information for individuals and researchers.