The Internet of Things (IoT) is expected to include billions of tiny devices that collect, process, and communicate sensory data. As of now, batteries power these devices. Batteries, however, are large, expensive, and short-lived - even the rechargeable ones wear out in a few years. Therefore, they are not a sustainable powering solution. Tiny battery-less devices promise a maintenance-free and environment-friendly alternative. They operate by harvesting energy from the environment. Ambient power, however, is marginal and unpredictable. This causes tiny energy-harvesting devices to operate intermittently, violating the requirements of many real-world applications. This work presents an event-based command-recognition algorithm tailored towards battery-less sensors, taking into account the challenges of intermittent execution and the ultra-low-power hardware. Our algorithm achieves a 97% recognition accuracy with a ten-word vocabulary.