Google Inc. is expected to disclose details about how consumers will be able to make store purchases, redeem coupons, and get loyalty points by waving smartphones in front of a small reader at the checkout counter, said people familiar with the matter.

At an event Thursday in New York, the Web-search company is planning to show off the technology, called near field communication, which is embedded in newer smartphones powered by Google's Android software and that can help turn the devices into a kind of electronic wallet,...