Disclosed herein are sensors that include: (a) a circuit board that includes an electronic processor； (b) a plurality of radiation sources, each source being attached to the circuit board； and (c) a spectral detector attached to the circuit board, the spectral detector being configured to analyze radiation derived from one or more of the plurality of radiation sources. During use, the sensors are configured to be worn on a portion of a body of a subject. The electronic processor is configured to cause two or more of the plurality of radiation sources to direct incident radiation to the subject, to cause the spectral detector to analyze radiation from the subject, and to determine one or more properties of the subject based on the radiation from the subject. Methods of making and using these sensors are also disclosed.
