I. Introduction
There is an emergingtrend in the healthcare industry to apply the advances in ubiquitous computing and sensor technology to provide continuous monitoring of a patient's medical condition anytime and anywhere. Numerous sensors and actuators have been developed for monitoring physiological parameters including pulse, heart-rate, oxygen saturation, as well as behavioural parameters such as posture and gait [1]. These sensors and actuators, which are usually wearable and often implantable can form a body sensor network using wireless communications. They can also interact with wearable processing units such as PDAs, mobile phones, and the fixed network infrastructure in the environment, thus providing a platform for continuous monitoring of the patient's vital signs. The body sensor network is particularly useful for monitoring patients in post-operative care or with episodic manifestations (such as cardiac arrhythmia). The benefits to the patients include early release from hospital, and early detection of abnormal conditions. Automated alerts to healthcare personnel can also be used to obtain help in the event of significant deviations from the norm or medical emergencies [2].