SAN FRANCISCO — Get ready to say good riddance to the checkout line.

A year after Amazon opened its first cashier-less store, startups and retailers are racing to get similar technology in stores throughout the world, letting shoppers buy groceries without waiting in line.

If they work, cashier-less stores will not only save time but maybe money too. From cameras and sensors, the stores will know when shoppers pick up a product and put it down, and can send them a discount to tempt them to buy it. Merchants will receive more insights into how people shop. They can create more space for merchandise, better track when shelves need replenishing and draw more business from the hordes of customers who detest long lines.

Amazon has a head start, opening 10 convenience stores in Chicago, San Francisco and Seattle. Several startups are pitching technology to retailers who want to create similar stores. Companies including AiFi, Zippin, Grabandgo, Trigo Vision and Inokyo say they are negotiating deals with retailers in the United States and other parts of the world, although none are ready to identify them yet.

"Once a few big retail chains begin to deploy this technology, it's going to snowball and we will see more and more of them doing it," says Michael Suswal, co-founder of Standard Cognition, another cashier-less technology startup.

But the monitoring system underlying cashier-less technology is bound to raise new privacy issues and worries about customer data falling into the wrong hands, especially if stores deploy facial recognition software in the omnipresent cameras watching shoppers.

"It could be scary, and it could be creepy," says Peter Trepp, CEO of FaceFirst, a Los Angeles company that so far has only sold its facial recognition tools to retailers trying to identify shoplifters and other criminals.