Among numerous sensors and alarm systems for the Internet of Things (IoTs), an alarm system for geological disasters or falls directly relates to the safety of people's lives and property. However, the energy supply and complex signal processing limit their wide application and reliability. As an emerging new energy technology, triboelectric nanogenerators (TENGs) can be used as a sensor power supply or even an active self-powered sensor. Unfortunately, for the existing alarm systems based on TENGs, the signal intensity change caused by the occurrence of danger is still limited, making the method of simply judging whether the signal strength exceeds the threshold to alarm not so reliable. Herein, a dynamic electrode for switching high and low output voltage is demonstrated. By introducing short-circuit and air breakdown effects through the novel dynamic electrode, the output voltage of this kind of device in the trigger state is nearly three orders of magnitude higher than that in the normal state. Based on the dynamic electrodes, a series of portable and wearable alarm systems are developed and applied to the fall-down alarm system and rockfall alarm system. Therefore, this work offers a new strategy to improve the reliability of alarm systems for geological disasters or falls and exhibit immense potential in the field of protecting people's lives and property.