Wearable pressure sensors have obtained significant interests owing to their diverse applications in electronic skins and smart health informatics. Ultrahigh sensitivity, wide linearity, and better pressure resolution are highly desirable attributes of the pressure sensors for versatile applications. Here, a flexible supercapacitive pressure sensor (SPS) based on a novel reversible ion pumping mechanism is reported that remarkably increases the pressure sensitivity over a broad linear range exceeding the limits of the existing iontronic pressure sensors. The SPS is composed of lower concentration ionic nanofibrous membrane between two graphene-polymer nanocomposite electrolyte films, which engages in ion pumping, triggering a high electrical double layer capacitance under external stimuli. The fabricated SPS exhibited an ultra-high sensitivity of 9029 kPa−1 over wide linear range (0–100 kPa) with outstanding pressure resolution of 0.446%. Additionally, a wireless fitness tracker system is successfully demonstrated by integrating the SPS, which can monitor the food consumption and posture of users to improve their lifestyle.