A system and method for monitoring stocked shelves is disclosed. A shelf monitor comprising an array of sensors id deployed in proximity to a stocking shelf and so that the sensors face a region on the stocking shelf containing shelved goods. A CPU module is configured to receive outputs from the sensors and execute a detection algorithm to detect a change event in the shelved goods and an algorithm to train the detection algorithm. Shelf monitors can be used in multiple numbers; a master shelf among the shelf monitors serves to aggregate data and local control of the system. A master controller can establish communication with a cloud server, allowing many additional features such as integrating the shelf monitoring system with inventory and point-of-sale databased.