<p>Conductive hydrogels derived from natural polymers have attracted increasing attention in wearable electronics due to their inherent biocompatibility and sustainability. However, their poor mechanical strength, limited conductivity and unsatisfactory environmental adaptability remain significant challenges for practical applications. In this study, we report a high-performance gelatin-based conductive hydrogel (GPC) reinforced with polypyrrole-decorated cellulose nanofibers (PPy@CNF) and enhanced by a zwitterionic betaine/(NH₄)₂SO₄ solution. The PPy@CNF hybrid nanofillers were synthesized <i>via in situ</i> oxidative polymerization, enabling homogeneous dispersion of PPy along the CNF surface. The incorporation of PPy@CNF significantly improved both mechanical strength and conductivity of the gelatin hydrogel. Meanwhile, the Hofmeister effect induced by (NH₄)₂SO₄ strengthened the hydrogel network, and the introduction of betaine further enhanced its anti-freezing and moisture-retention properties. The optimized GPC hydrogel exhibited a high tensile strength of 1.02 MPa, conductivity of 1.5 S·m^-1, and stable performance at temperatures down to -50 °C. Furthermore, it was successfully assembled into a wearable strain sensor for real-time human motion monitoring, and as an electrode layer in a flexible triboelectric nanogenerator (TENG), enabling biomechanical energy harvesting and self-powered sensing. This work provides a promising strategy for developing sustainable, multifunctional hydrogels for next-generation wearable electronics.</p>