Obstructive sleep apnea (OSA) is the essential cause of sleep-related breathing disorders in which breathing repeatedly stops and starts during sleep. Sleep-disordered breathing can affect our overall health, safety, and quality of life. This study was focused on the detection of sleep posture and sleep breathing disorder, by measuring the sensing response of a piezoelectric sensor installed on the mattress, pillowcase, and sleep apnea positional-therapy device. In this work, we have developed a sleep monitoring system based on an unobtrusive method. The results of sleep efficiency, sleep pose, and sleep apnea was compared with the gold standard of sleep monitoring in-laboratory polysomnography (PSG). Linear regression of all results reveals strong correlations between our smart sleep system and the PSG device. This novel system has high efficiency as an alternative not only to monitor sleep but also to identify and treat abnormal breathing patterns by training to sleep on your side positions. It can help improve the quality of sleep and reduce snoring and sleep apnea.