Remote and online patient monitoring can significantly reduce the cost for the health care system. Body Sensor Network (BSN) plays a key role in real-time remote health monitoring. Although the BSN can reduce the health monitoring cost, some technical challenges arise. One of the major challenges in BSN is the power consumption. The power recharge is very difficult and inconvenient in BSNs. Therefore, energy saving is one of the most appropriate approaches to prolong the network lifetime. In the thesis, we propose a context-aware Medium Access Control (MAC) design to extend the network lifetime of the BSN. The proposed MAC reduces data transmission by determining the more valuable fraction of data. The high-value portion of the data is transmitted, while the low-value fraction of the data is omitted, at the sensor node. The simulation results demonstrate that the proposed method can reduce the transmission energy by up to 30% compared to the existing method called burst communications.