We target body-wearable sensor networks, in which sensor nodes are strategically placed on the human body and the wireless communications are conducted on/off the surface of the body. The results, obtained by performing multiple experiments in outdoor environments, are presented. A single on body transmitter communicates with a single receiver node, which is located on the body or off the body at various distances. Sensor nodes utilized in our experiments are equipped with XBee and XBee Pro wireless modules for on body and off body communications, respectively. The focus of our work is to observe how the Received Signal Strength (RSS) and the Packet Reception Rate (PRR) vary as we change the communication distance and transmission power level. Our experimental results can be used to perform transmission power control with high precision in order not to exceed a certain packet error rate.