An inventory management system includes a beacon or button connected to a warehouse server. The beacon buttons are placed in or near a product storage area with a number of products. The beacon has a controller and a transceiver to communicate with a server. There is a user input on the front of the beacon and several sensors able to detect a user identity and interaction with the products. When the user input is triggered, the beacon sends a message to the warehouse server including a user identity and other sensor data. Additionally, the beacon includes an energy harvester configured to power the beacon from ambient or user provided energy.