Using technology invented at MIT, doctors may one day be able to monitor patients’ vital signs by having them swallow an ingestible electronic device that measures heart rate and breathing rate from within the gastrointestinal tract. This type of sensor could make it easier to assess trauma patients, monitor soldiers in battle, and perform long-term evaluation of patients with chronic illnesses. For the military, this kind of ingestible device could be useful for monitoring soldiers for fatigue, dehydration, tachycardia, or shock. When combined with a temperature sensor, it could also detect hypothermia, hyperthermia, or fever from infections. The new sensor calculates heart and breathing rates from the distinctive sound waves produced by the beating of the heart and the inhalation and exhalation of the lungs. Through characterization of the acoustic wave, recorded from different parts of the GI tract, the MIT researchers found that they could measure both heart rate and respiratory rate with good accuracy. The entire sensor is about the size of a multivitamin pill and consists of a tiny microphone packaged in a silicone capsule, along with electronics that process the sound and wirelessly send radio signals to an external receiver, with a range of about 3 meters.