This lecture covers the physiology aspects of blood oxygen content, the key role of oxygen in aerobic metabolism, hypoxemia consequences, spectrophotometry, pulse oximetry technical descriptions, limitations, future perspectives, and clinical applications. It also delves into the market size, specifications, integration of pulse oximetry in smartwatches, and the global demand for pulse oximeters. The presentation discusses the mechanisms of glucose monitoring devices, including paper-strip-based technology, implantable micro fluorometers, continuous glucose monitoring, and the comparison of different technologies. It concludes with a showcase of data and future developments in glucose monitoring devices.