The Internet of Things (IoT) has become a promising technology that is making the interaction between humans and physical objects autonomous and intelligent. It has been driving a massive transformation of modern society and applications, such as wearable sensing, smart campus monitoring, and healthcare monitoring. However, there are still some challenges in IoT applications, such as providing long-term and reliable energy supply for IoT sensors, designing better wearable sensors for safety and vital signs monitoring, and integrating heterogeneous devices at the edge. This presentation will begin with a brief overview of IoT applications in the fields of environment, safety and healthcare monitoring. Following that, some self-powered IoT sensors for diverse applications will be presented. Next, some healthcare-related IoT sensors for safety and vital signs monitoring will be discussed. Then, certain IoT applications facilitated by edge computing and wearable IoTs will be described. Finally, future research directions will be presented.