Yelp started allowing users to check-in at different businesses about a year ago. Now the user-generated review site is now offering business owners a chance to hook loyal users with special promotions via its new "Check-in Offers" service.

"This new feature within the business owner dashboard allows you to reward customers with a coupon when they 'check-in' to your business," Luther Lowe, business outreach manager for Yelp, said in a blog post. "It provides a measurable way to reward your most loyal customers while attracting new ones."

Business owners can either offer a percentage off certain goods or free and fixed price offers. Users can unlock these promotions when they check-in at a business via Yelp's smartphone app and use the virtual coupon then or save it for another time. If it's saved, it will stay on the business's page, in the user's "About Me" page, or at the check-ins tab on the Yelp app.

Yelp isn't the first social service to offer promotions for users who turn up at a participating business. Location-based pioneer Foursquare has had this feature for quite a while, and Facebook jumped on the bandwagon earlier this month with Facebook Deals. To learn more about that service, check out PC Mag's hands on.

Although a recent Pew study reported that only 4 percent of adults use location-based services, Foursquare said that it's grown significantly in the past year - from 100,000 to over 4.5 million users. As a result, the company will open a San Francisco office. "We've been working out of the Square office for some time now (they're awesome!), and they've been nice enough to free up more room for us to hire a full team of West Coast engineers," Foursquare said in a blog post.