In this demonstration we present an ubiquitous health monitoring system based on the NGN/IMS (Next Generation Network/IP Multimedia Subsystem). It enables us to be taken care of by medical professionals anytime, anywhere using portable medical sensors and mobile networks. To provide seamless health monitoring services, an open, secure and functional platform is required. Such a platform should support multiple functions such as real-time transfer, event notification, and continuous data accumulation. The NGN/IMS is a potential platform to fulfill these requirements, because it is a standard-based open platform, which provides AAA (Authentication, Authorization and Accounting), QoS (Quality of Service) support, event notification and a data management server. We present a system design and a prototype implementation on a NGN/IMS testbed.