Ambient energy harvesters show great potential for powering distributed sensor nodes. However, their output performance is often limited by single-source energy, resulting in poor adaptability, stability, and energy utilization ratio under variable weather conditions. Herein, a high-adaptability ambient energy harvester enhanced by a bi-concave flow amplifier is proposed. The omnidirectional airflow smoothing enhancement design of the amplifier is inspired by the canyon effect. And the inclined surface of the amplifier offers building-block-like modular assembly, enabling synergistic non-invasive integration of electromagnetic–photovoltaic–triboelectric effects. The results indicate that the amplifier boosts the wind energy harvesting efficiency by 86.87% and reduces the start-up wind speed to 0.4 m s−1. Within the theoretical–simulation–experimental framework, the measured power densities reach 14.158 W m−2 (wind), 63.47 W m−2 (solar), and 25.42 W m−2 (raindrop), demonstrating robust performance across varying weather conditions. Notably, leveraging the multi-energy sensing capabilities of the harvester, a self-powered weather warning system and an automated smart greenhouse control system have been developed. This system-level application offers a new perspective for the deep integration of energy harvesters with smart agriculture.