The objective of this paper is to present the recent development of the ring sensor to monitor a patient 24 hours a day for a tele-nursing system. The ring sensor is worn by the patient at all times, hence the health status is monitored 24 hours a day. The sensors packed into the ring include LEDs with different wavelengths, and technologies of photoplethysmography [1-2] and pulse oximetry [3-4] are implemented on the ring. The sensor data are transmitted to a computer through the digital wireless communication link and the patient status is analyzed continually and remotely. Any trait of abnormal health status and possible accidents is detected by analyzing the sensor data. A combination of a global receiver and multiple local ones are used to estimate the patient's location and activity, e.g. taking a shower in the bathroom, using a toilet, sleeping in a bed, and ascending/descending the stairs. Both the physiological data and the position information can be used to make an acc...