ExOsense is a liquid-level sensor that attaches to the outside surface of plastic bottles or containers and detects the presence or absence of fluid through the bottle wall. The liquid-level sensor is a non-intrusive unit for plastic fluid containers. It adheres to the outside of plastic bottles, via a peel-and-stick adhesive face and is unaffected by the color or transparency of the plastic. Liquids inside the bottle are untouched so there is no issue of material compatibility or contamination. The liquid-level sensor can fit to virtually any size or shape vessel, from small bottles to large tanks. It can be mounted anywhere on the outside of the tank to provide high, low, or any intermediate point level fluid sensing.