Want to have doctors wrapped around your finger? MIT mechanical engineers Harry Asada and Phillip Shaltis have developed a “ring sensor” that monitors the wearer’s temperature, heart rate, and blood oxygen level. About the size of a class ring, the device is equipped with two light-emitting diodes that beam pulses of red and near infrared light through the user’s finger. A detector on the opposite side of the ring measures the intensity of the transmitted light. Just how much light passes through depends on the oxygen levels and the volume of the blood in its path. Volume changes over the course of a heartbeat and can indicate small changes in heart rate. The battery-powered ring contains a wireless link that can transmit vital signs to a cell phone or computer, allowing a caregiver to determine remotely whether a patient needs assistance. The ring could be used in emergency rooms to monitor patients waiting for treatment, in homes to watch patients after heart surgery, and even in cars to check drivers’ fatigue levels. The researchers have finished a round of clinical tests and are working with companies to commercialize the device within five years.