Development in low-power integrated circuits, ultra low-power RF (radio frequency) technology, wireless communications and micro sensors permitted the realization of Wireless Body Area Networks (WBANs). It is one of the latest approaches in medical identification, management and also key building block for future intentional networks and Internet. Wireless BAN has a capability to process and communicate data of heart beat, motion, respiration, body temperature, sound, vibration and blood pressure. This paper presents a comprehensive discussion on the applications of WBANs in various endeavors of life. Also highlighted are a number of projects that enable WBANs to provide unobtrusive long-term healthcare monitoring with real-time updates to the health center. In addition, we list many potential medical applications of a WBAN including epileptic seizure warning, glucose monitoring, and cancer detection.