Flexible wearable humidity sensor (HS) has become indispensable in various fields such as man–machine interaction, biomedical applications, and industrial environmental monitoring. In particular, the HS powered by supercapacitor (SC) can meet the demand of environmental protection. In this study, an integrated SC and HS system (SCHS) based on the bifunctional material NiCo2O4/g-C3N4 is proposed. Additionally, a humidity signal detection and wireless transmission device is developed to match SCHS. The large surface area of g-C3N4 provides a significant number of surface-active sites that facilitate its synergistic effect with NiCo2O4, which has high electrochemical activity and excellent conductivity. Their synergistic effect makes g-C3N4/NiCo2O4 nanocomposites not only show remarkable sensitivity (1471 kΩ/% RH@11 % RH) to humidity sensing, but also show ultra-high specific capacitance (1061F g−1@0.5 A g−1 current density) on supercapacitors. The SCHS with excellent performances is used for non-contact human–computer interaction, respiratory monitoring of patients with respiratory diseases and humidity monitoring in hazardous industrial environments. In addition, a freestanding-rotation-disk (FRD-TENG) is used as a backup power supply for humidity monitoring system and wireless transmitter module in emergency situations. This work provides a universal and effective strategy for reducing the spread of infectious diseases and protecting lives and property.