Breathing, as a vital physiological parameter, holds significance in reflecting the breathing abnormalities associated with sleep apnea syndrome (SAS) through real-time breathing monitoring. Stretchable strain sensors, designed to match the strain patterns of chest and abdominal movements that accompany breathing, can deform to the maximum extent along with the thoracic and abdominal changes, thereby capturing the intricate details of breathing state variations. In this study, we commence with strain sensors to explore and develop a portable, user-friendly, and cost-effective wearable equipment for real-time breathing monitoring. A core-shell elastic thread composed of a hydrophilic shell and an elastic core is utilized as the substrate, a strain sensor is constructed through a simple immersion method, and carbon-based materials are loaded onto the hydrophilic shell layer. The sensor benefits from the unique weaving structure of the shell, exhibiting a high gauge factor (GF) (25.8) and linearity (0.998) within a strain range of 0%–50%, along with excellent stability (>20 000 cycles). Integration of the sensor into a system yields a wireless breathing monitoring device capable of real-time tracking of breathing rate and status. This comprehensive research covers the entire development process, encompassing sensor fabrication, software development, and a specific focus on sleep apnea applications.