In Sweden* (and surely other places) you borrow a portable barcode scanner when you enter the store and scan your own products. At the end the cashiers take the scanner and do something and you're done.
I think they do random "bag checks" as well every now and then. And you might need to have the stores credit/debit card (but I am not sure because I never used this system myself).
I know of one chain here in Norway that does this, but only in a few of their larger stores. I believe you have to set up a card with them that is connected to your bank account. They have regular lines as well for the folks that don't do this.
I somewhat assume that when this becomes cheap enough, some version of it will be in all the places, probably in conjunction with something that weighs the cart or basket to see if it matches up to what you have scanned.
I think they do random "bag checks" as well every now and then. And you might need to have the stores credit/debit card (but I am not sure because I never used this system myself).
Here are some pictures https://www.google.co.th/search?q=ica+bar+kod+skanner&source...
* In the main brand supermarkets at least.