A device which detects or senses liquid level in a beverage containment vessel, and produces either light, audio or a data output based on the liquid level being equal to or less than a predetermined level. The device, in practice, preferably retains the shape of the beverage containment vessel (e.g., cylindrical), and have an outer housing of opaque or semi-translucent material. The device is either integrated into a new beverage containment vessel, or retrofitted to existing vessels. The device is powered by battery, and can be switched on, off, or into various operating modes by internal switching mechanism.