In the context of an aging society, triboelectric nanogenerators (TENGs) have emerged as promising wearable monitoring devices for the elderly owing to their dual functionality in energy harvesting and sensing. However, achieving high power density and long-term stability remains a challenge. Here, three stable triboelectric materials with enhanced surface potential are designed and synthesized using a cation-induced strategy based on ion exchange with Keggin-type PW12 (H3PW12O40·nH2O). Among these, the K+-induced rhombic dodecahedral PW12-1 demonstrated optimal performance. The resulting TENG-1 demonstrated a remarkable output voltage of 147.8 V, a current of 716.8 nA, and a power density of 0.193 W m−2, representing a 4.2- to 9.2-fold improvement over pristine PW12. Furthermore, the device displayed exceptional stability, maintaining 95% of its initial performance after 10 000 s and 10-day of continuous testing. Mechanistic studies revealed that the enhanced triboelectric performance is attributed to increased surface roughness (≥3.46 nm) and elevated surface potential (≥2.03 V). The optimized TENGs successfully distinguished the various motion patterns of the elderly (walking, sudden stop-continued walking/falling), while providing real-time risk alerts through voltage signals. This study provides valuable insights for the development of advanced wearable smart monitoring systems and contributes to the advancement of intelligent elderly care technologies.