"From infrared radiation in the user’s ear, sensors… can detect minute temperature variations due to the user’s heart beats," the application reads. "Heart rate can be calculated based on time between beats and the user’s temperature can be set as the ‘DC Component’ (or average or median value) of the detected temperature distribution. Other sensors can also be used for tracking the same physiological metrics or different physiological metrics."
In another example, a light source and photodetector allow the hardware to determine a user’s blood oxygen content. Such a system would “detect the portion of such light that passes through the user’s earlobe, the remaining light having been absorbed within the user’s earlobe. From the relative absorption of these two wavelengths of light, the user’s blood oxygen content can be calculated.”