Amazon has patented designs for a wristband that can precisely track warehouse employees’ location and lead warehouse workers’ movements with the use of vibrations. The theory relies on ultrasonic sound pulses to detect the position of an employee’s hand about a series of inventory bins. The wristbands according to the patent documents,  are designed as a labor-saving measure to keep track of products throughout the warehouse. One of the patents outlines a haptic feedback system that would vibrate against the wearer’s skin to point their hand in the right direction.

The concept, which aims to streamline the fulfillment of orders, adds another layer of surveillance to an already challenging working environment. When someone orders a product from Amazon, the details are transmitted to the handheld computers that all warehouse staff carry. Upon receiving the order details, the worker must rush to retrieve the product from one of many inventory bins on shelves, pack it into a delivery box and move on to the next assignment.

Amazon has not announced plans to introduce the wristbands in warehouses at this point, but the news of the patents comes after several other measures the company has taken to track its employees. According to a media report, to hit targets for packaging and delivering orders, British warehouse workers are reportedly subjected to timed bathroom breaks and electronic timers to monitor how many boxes they pack per hour during their 55-hour workweeks.