Sensing the liquid level in a container is critical to building many smart home and mobile healthcare applications. This paper presents a liquid level sensing system that is low-cost, high accuracy, widely applicable to different daily liquids and containers, and can be easily integrated with existing smart home networks. Our system uses an existing home WiFi network and a low-cost transducer that is attached to the container to sense the resonance of the container for liquid level detection. We evaluate our system in home environments with various containers and liquids. Preliminary results show that our system achieves an accuracy of 97% for continuous prediction and an F-score of 0.968 for discrete prediction.