The present disclosure relates to an optical sensing accessory, an optical sensing device, and an optical sensing system. An optical sensing accessory, an optical sensing device, or an optical sensing system comprises a plurality of reflective optical sensor modules (109) and other electronic modules to achieve multi-site measurement. A reflective optical sensor module comprises a light source, a photodetector, and a substrate. The light source is configured to convert electric power into radiant energy and emit light to an object surface. The photodetector is configured to receive the light from an object surface and convert radiant energy into electrical current or voltage. Multi-site sensing devices (16) improve measurement accuracy and user compliance to record their physiological condition.
