An improved sensor (102) for respiratory and metabolic monitoring in mobile devices, wearables, security, illumination, photography, and other devices and systems uses a broadband ambient light (114), which is then transmitted to a target (125) such as the ear, face, or wrist of a living subject. Some of the scattered light returning from the target to detector (141) is passed through spectral filter set (155) to produce multiple detector regions, each region sensitive to a different narrowband wavelength range, and the detected light is spectrally analyzed to determine a measure of a physiology of the subject such as pulse, respiration, hydration, calories. Additional broadband light can be added when ambient light alone may be sufficient illumination for analysis. The same sensor can provide identifying features of type or status of a tissue target, such as respiratory rate depth, heart rate variability, heart function, lung function, fat content, calories used or ingested, or even confirmation that the tissue is alive. Monitoring systems incorporating the ambient light sensor, as well as methods, are also disclosed.
