Ultrasensitive mechano-stimuli photoluminescence enhancement was observed in pyramid-like zinc oxide nanoparticles (ZnO NPs), which are fabricated by a facile hydrothermal route. The response of the ZnO NPs to mechanical stimuli is so sensitive that even an ant walking and acoustic vibration can trigger the luminescence enhancement. The mechanism for this unusual behavior was attributed to the electron injection process between crystal boundaries. Thus, this work opens up the possibility of detecting slight mechanical stimuli wirelessly, rapidly, and sensitively. Importantly, the sensitive response of the NPs to sound waves can find potential application in devices for hearing-impaired people.