The aim, Amazon says in the patent, is to streamline “time consuming” tasks, like responding to orders and packaging them for speedy delivery. With guidance from a wristband, workers could fill orders faster.

Critics say such wristbands raise concerns about privacy and would add a new layer of surveillance to the workplace, and that the use of the devices could result in employees being treated more like robots than human beings.

Current and former Amazon employees said the company already used similar tracking technology in its warehouses and said they would not be surprised if it put the patents into practice.

Max Crawford, a former Amazon warehouse worker in Britain, said in a phone interview, “After a year working on the floor, I felt like I had become a version of the robots I was working with.”

He described having to process hundreds of items in an hour — a pace so extreme that one day, he said, he fell over from dizziness.

“There was no time to go to the loo,” he said, using the British slang for toilet. “You had to process the items in seconds and then move on. If you didn’t meet targets, you were fired.”

He worked back and forth at two Amazon warehouses for more than two years and then quit in 2015 because of health concerns, he said: “I got burned out.”