The Yelp Inc. app is used to search for taco locations in New York © Scott Eell, Bloomberg via Getty Images

Restaurant apps such as OpenTable and Urban Spoon have been around for a while, but competition is heating up as some tech industry giants make a play for the hearts and stomachs of millions of mobile diners.

Today, you can use apps to find restaurants by you, browse their menus, order take-out, get meals delivered and rack up points at your favorite eateries toward discounts or free goodies. In some cases, you can even pay with your phone.

Restaurants are going mobile in an effort to better promote themselves to repeat customers and would-be patrons. In recent months, Facebook, Google, Yelp and other big tech and restaurant industry companies are jumping in to help.

For restaurants, putting up-to-date menu information online and signing on with services that let diners make reservations or order from their phones is just "the ground floor," says Jim Williams, a long-time industry observer and the chief executive at MustHaveMenus, an Ashland, Ore., menu design, printing and marketing company with 30,000 restaurant customers. "We have a long way to go. These bells and whistles like easy payment and loyalty programs will accelerate usage of mobile."

Here's a peek at some of the most recent developments, and what they mean to diners:

Facebook: The giant social network this month started offering users of its iPhone and Android mobile apps the ability to make reservations at more than 20,000 restaurants in the United States and Canada through a partnership with OpenTable, the popular online booking service.

Google: Late last month, Google relaunched Zagat, the restaurant-rating service it bought two years ago, as a free website and mobile app for Android and iPhone devices. In response to early criticism from some reviewers, Google has already revised the app so users can search restaurants in 40 cities by rating, cuisine and neighborhood, as well as via a map search.

Yelp: The popular user recommendation service bought an online reservation startup called SeatMe in July. Now when you find a yummy-sounding Thai or Tex-Mex restaurant on Yelp, you can book a table for two without leaving the site. Yelp previously struck deals with delivery services and Eat24 that allow users to place restaurant to-go orders directly from the site.

Starbucks: Starbucks was one of the first major chains to create an app that connects its frequent-user loyalty program with mobile payments and a store locator. Now, if you walk into a Starbucks, you can order a latte, get points toward free drinks and pay for your order by swiping your phone. More than 10% of the coffee chain's in-store transactions are made via mobile phones, a Starbucks executive said during a third-quarter earnings call in late July. "I never pull out cash at a Starbucks," says Williams, of MustHaveMenus. "I get free drinks. I can find a Starbucks close to me in two seconds. It creates a better experience for me, and for Starbucks. That's going to be true of any restaurant, especially the chains."

Loyalty apps: Restaurants that aren't big enough to run their own loyalty programs can sign up with one of more than 30 mobile loyalty programs that have popped up in recent months, according to a Wall Street Journal report. Loyalty app provider Front Flip, which has 2,000 restaurant partners, lets diners scan a code on display in a restaurant to unlock a digital scratch card good for free or discounted menu items, according to the report. Belly, another loyalty app, gives restaurants an iPad with a special program and bar code that customers can scan with their smartphones phones to track points toward rewards, according to the report.

Restaurant-specific apps: Upscale restaurants and fast-food chains such as Wendy's, Five Guys, Jimmy John's Gourmet Sandwiches and Dominos Pizza have apps that allow users to look up menus and, often, to order online. The My Wendy's app also shows calorie counts for menu items and was updated recently to take mobile payments. The Dominos app lets users order and pay for delivery or take out; it also lets them track their order to find out when it's being made and delivered.

Williams predicts more restaurants will follow, and not just big chains. "There's a trend toward local restaurants having an app," he says. "I'm not saying they're all going to have one. But the strong local restaurants may end up either being part of a select app that helps people navigate a certain region or type of food, or they'll have their own app."

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Apps aren't the only way restaurants are using mobile-based services to keep customers in the know about specials. Rita's Italian Ice, a Trevose, Pa., chain with 600 locations in 20 states, lets customers sign up for Cool Alerts to have text messages or email alerts sent to their phones when their local Rita's has a favorite flavor in stock.

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