A device to measure the material level inside the container includes a housing unit removably attachable to a cap of a container for holding a beverage, wherein the housing unit is configured to remain attached to the cap when the cap is at least partially removed from the container. The device further includes, a signal producing unit located in the housing unit, a first sensor located in the housing unit to sense a beverage level in the container and a controller located in the housing unit. The controller is configured to receive from the first sensor an indication of a beverage level in the container and activate the signal producing unit based at least on the indication of the beverage level in the container.