Effectively harvesting ambient energy is a key approach for realizing self-powered systems for portable electronics, wireless sensing, implanted devices, security and so on. It is generally desired that adding a power harvester should not add much weight, volume or additional components to the electronics. In this work, a cover-sheet-based (CS) triboelectric nanogenerator (TENG) is developed based on the protection structure of an electronics, such as a smart phone, for generating power for mobile electronics through conversion of mechanical energy. It consists of a slider and two stators. Each stator comprises of two complementary micro-grating electrodes. At a sliding velocity 1ms−1, the CS-TENG produces an output current of 88.8μA, and a voltage of 2372V. As a thin cover for mobile electronics, under the hand motions, the CS-TENG can light up household light bulbs or directly driving a mobile temperature meter without the use of a battery. In addition, springs are added to make the CS-TENG suitable for scavenging vibration energy from body motion. This study immediately opens the applications of TENG for conventional sensor systems.