To improve the unobtrusiveness and comfortableness of sleep monitoring, we proposed the design and implementation of a smart mat which utilized flexible pressure sensor array and printed electrodes to monitor physiological and behavioral data during sleep. With the proposed novel soft seven-layer structure, the smart mat system can measure pressure distribution images and calculate respiratory rate of subjects. The function of this system was realized with pressure acquisition circuit controlled by Arduino processor. Experiments for pressure distribution tests and respiratory rate measurements were carried out to validate the performance of the proposed system. The experimental results demonstrated that the smart mat could be a viable option for unobtrusive sleep monitoring in the future.