Regular monitoring of blood oxygen saturation (SpO2) level and heart rate is critical not only during surgeries and in ICUs but also at home, especially for patients suffering from Chronic Obstructive Pulmonary Diseases. Reflectance pulse oximetry removes the hassles of probe based transmittance techniques and has the potential to emerge as the primary method for SpO2 measurement, especially for wearable and minimally intrusive physiological monitoring. Reflectance pulse oximetry at the finger can be used for intermittent monitoring applications by integrating the modality to life style devices like wrist watches. A wrist-worn finger based reflectance pulse oximeter which works in conjunction with a smart phone/tablet for cloud connectivity is presented. This paper describes the proposed system architecture and the data collection exercise carried out at high altitudes to obtain the calibration coefficients for device operation. The data collected during the high-altitude exercise was analyzed to verify the correlation between R values obtained from the device and the reference SpO2 measurements made using a standard equipment. The performance of the device was tested on 3 volunteers at heights of 5,360 m and 4,259 m from the sea level. © 2017 IEEE.