The purpose of this project is to integrate the technologies of wireless sensor networks and public communication networks to construct a healthcare system for senior citizens at home without interfering their daily activities. This system provides 4 main functionalities, including indoor monitoring, outdoor monitoring, activity and health state decision, emergency decision and alarm. JTH has developed a prototype of wireless sensor networks, an interconnection platform and a service management platform to support large scale data interconnections and real-time activity and health state reports to related persons (e.g. doctors or nurses, elder-self, elders’ relatives) via all popular communication approaches, such as automatic voice telephone call, SMS or Email etc. In this paper, the system functions and implementation approaches are introduced. A series of experiments results shows that the system performs high validity and reliability.