Sam's Club has a similar system on line now too. It's an app that you install on your smartphone. You scan each item into the app as you put it into your cart, then hit the "checkout" button to verify your payment. You show your phone to the receipt checker at the door, who scans it with a handheld scanner to verify that you paid for everything in your cart, and you are done.
IMO, it's not a bigger threat to employees than the self-checkout kiosks. It simply reduces the utilization of the self-checkout lines, reducing the maintenance costs of that hardware and saving the company money. There is still the same person at the exit doors validating the items in the cart match the receipt (mostly a simple count of items).