Proteus Digital Health has developed a system consisting of a smartphone, and a pill. Each pill contains a sensor that is coated in two digestible metals. These metals are not dangerous to consume because they currently exist in multi-vitamin supplements, as well as naturally in our diets. The pill transmits a signal once swallowed, to a small, battery-powered patch worn on the user’s torso and sends the data via Bluetooth to a caregiver’s or family member’s smartphone.
Recover, from Proteus. "Intended for use by athletes for surveillance of physiologic information." Patch to monitor heart rate, heart rate variability, respiration rate, skin temperature, activity, body posture, sleep, energy expended (kcals). Provides "recover score." See http://www.proteus.com/technology/proteus-recover-for-elite-athletes/