A versatile optoelectronic device with ultrasensitive negative-positive pressure sensing capabilities, which is integrated with a wireless monitoring system, was fabricated and demonstrated in the current work. The device comprises a monolithic GaN chip with a polydimethylsiloxane cavity and nanograting, which effectively transduces pressure stimuli into optical changes detected by the GaN chip. The developed device exhibits an ultra-low detection limit for a mass of 0.03 mg, a pressure of 2.94 Pa, and a water depth of 0.3 mm, with a detection range of -100 kPa to 30.5 kPa and high stability. The versatility of the device is demonstrated by its ability to monitor heart pulse, grip strength, and respiration. Its integration with a wireless data transmission system enables real-time monitoring of human activity and heart rate underwater, making it suitable for precise measurements in various practical applications.