“…Binu et al [9] proposed a monitoring system using a thermal flow sensor, tri-axial accelerometer, and photo electric sensor to measure the air flow, the body posture, and the oxygen saturation, respectively. In 2014, Rong et al [10] integrated 3 micro sensors with mobile communication devices including hotfilm flow sensor, accelerometer, and oximeter. They built a real-time system for monitoring and diagnosing obstructive sleep apnea.…”