Restaurants are increasingly exploring how location-based social networks like Foursquare can help build customer traffic.

With consumers’ increased adoption of smart phones that are able to find a user’s location and offer nearby promotions, restaurants chains — from casual operators Kona Grill, Chili’s Grill & Bar and Red Robin, to quick-service players like Starbucks, Pinkberry and Pizza Hut — are finding a growing consumer base.

Many of these restaurants are partnering with Foursquare, which has been adding 100,000 users a week and passed the 2 million-user mark in mid-July. The consumer network allows users to become “mayors” of sites if they have the most check-ins, and offers “badges” as a reward based on check-ins from numerous locations. Other location-based networks include Gowalla, Whrrl, Loopt, MyTown and Brightkite.

Chili’s Grill & Bar began offering Foursquare-using guests free chips and salsa for a limited time last month for merely checking in at any of Chili’s more than 800 corporate locations. To redeem the offer, guests simply show their waiter their phones after they have checked-in with Foursquare.

Stacey Sullivan, a spokesperson for Chili’s parent, the Dallas-based Brinker International Inc., said the chain is seeing a 20-percent redemption rate among those checking in and redeeming their actions for the chips and salsa.

“We’re seeing excellent results on the campaign,” she said. “Guests are very excited. Every week since the Foursquare offer began, the number of check-ins has doubled.”

Jill McFarland, director of marketing at the Batrus Hollweg International consultancy, said Chili’s move was brilliant, as it encourages Foursquare users to check in regardless of whether they have a chance to become “mayor.”

“Sometimes people don't bother to check in if they think there isn't a chance of being the mayor,” she said. “[The Chili’s promotion] also keeps people from gaming the system, because they aren't rewarded for number of check-ins but simply for checking in while they are in the actual location.”

McFarland also noted that Chili’s is one of few operators to use a promo code to track sales of the offer. After customers display their check-in on the phone screen to the server, the waiter enters the code when ringing up the order. The Foursquare special that pops up on the user’s phone has even made waiter training easy, he said, as it says: “Chili’s servers, use coupon code #23 to redeem.”

Chili’s offer of a free item for checking in to Foursquare makes the promotion a more generous version of ones such as Starbucks’ $1-off and discount offers and Red Robin’s discounted burgers.

At Kona Grill, the 24-unit grill and sushi chain based in Scottsdale, Ariz., a systemwide “Swarm Party” is planned for Aug. 18. Foursquare users can earn a “Swarm” badge by checking-in to the same location at the same time with 50 other users.

Marc Buehler, chief executive of Kona Grill, said, “We know our Kona Grill guests are savvy with social platforms, and we’re embracing every opportunity to communicate with them.”

Kona Grill’s Swarm Party, which will be held from 7 p.m. to 9 p.m. local time, also includes a special sushi roll, named The Stinger, available during the event. The current mayor at each location will get a free order of The Stinger.

Cathy McPhillips, media-marketing manager for Kona Grill, said social media must be a two-way relationship between a brand and its customers.

“This was a great way for us to give back,” she said. “Starting the night of the Swarm Party, we will also begin our Mayor Rewards program, offering a free appetizer or sushi roll to the current ‘mayor’ anytime they visit.”

McPhillips said Kona Grill is tracking Foursquare check-ins and monitoring Facebook post reaction.

“We want to stay current and use social marketing as a guest service tool, more so than an advertising tool,” she said. “If Foursquare users Tweet their Kona Grill check-in, I respond to every Tweet thanking them for coming in and making sure they had a good experience.”

Contact Ron Ruggless at rruggles@nrn.com.