Abstract: A method includes receiving, at an inventory monitoring device and from a system including shelf inventory sensor devices that each include cameras and distance sensors positioned to monitor shelf spaces, camera image data and distance sensor data from the shelf inventory sensor devices. Types of items stored on shelf spaces and a number of items stored on the at shelf spaces are determined based on the camera image data. A current used volume of the shelf spaces is identified based on distance sensor data, and a notification is sent to a device associated with the supplier in response to a determination that the current used volume is lower than a predetermined threshold.