Significance: Oxygenation is one of the skin tissue physiological properties to follow for patient care management. Furthermore, long-term monitoring of such parameters is needed at the patient bed as well as outside the hospital. Diffuse reflectance spectroscopy has been widely used for this purpose. Aim: The aim of the study is to propose a low-cost system for the long-term measurement of skin physiological parameters in contact. Approach: We have developed a low-cost, wearable, CMOS-based device. We propose an origi- nal method for processing diffuse reflectance data to calculate the tissue oxygen saturation (StO2). Results: We tested the device for the assessment of tissue oxygenation during a first-in-human clinical trial that took place at the Grenoble University Hospital France. Conclusions: The results of this clinical trial show a good accordance between our sensor and commercial devices used a reference.