Benefiting from the widespread potential applications in the era of the Internet of Thing and metaverse, triboelectric and piezoelectric nanogenerators (TENG & PENG) have attracted considerably increasing attention. Their outstanding characteristics, such as self-powered ability, high output performance, integration compatibility, cost-effectiveness, simple configurations, and versatile operation modes, could effectively expand the lifetime of vastly distributed wearable, implantable, and environmental devices, eventually achieving self-sustainable, maintenance-free, and reliable systems. However, current triboelectric/piezoelectric based active (i.e. self-powered) sensors still encounter serious bottlenecks in continuous monitoring and multimodal applications due to their intrinsic limitations of monomodal kinetic response and discontinuous transient output. This work systematically summarizes and evaluates the recent research endeavors to address the above challenges, with detailed discussions on the challenge origins, designing strategies, device performance, and corresponding diverse applications. Finally, conclusions and outlook regarding the research gap in self-powered continuous multimodal monitoring systems are provided, proposing the necessity of future research development in this field.