Flexible health care service is a key driver in reducing expenditure and enabling improvements in disease management. Integration of modern wireless communication systems and sensor technology permit the real time acquisition, transmission and processing of critical medical information. Researchers have focused on streaming vital signs and physiological data over a wireless network to a central data server for medical decision making. Constraints in wireless data communication have been reported as the major impediment for using this technique, mainly because of the energy consumption. In this paper, we examine the optimal way of storing data and performing analysis on sensors and on the mobile device. We show that when a patient is mobile, a smart phone is the device best suited to perform the initial processing of vital signs and sending of medical alerts. A smartphone has sufficient storage and computational ability, if exploited appropriately, to process and store sensed data from multiple sources.