Unlike most app makers, Kudzu Interactive, which is based in Atlanta, is profitable, and its revenue grew fivefold last year, said Jim Garrett, its founder and chief executive. The Snapfinger app is free for diners, and Kudzu Interactive charges restaurants 3 percent to 10 percent of each bill. It makes money every time someone uses the app, not when it is first downloaded.

“A lot of people think of mobile companies as iPhone app developers who make a product and sell it for 99 cents,” Mr. Goldman said. “This is much more than that. It’s a new way to conduct a transaction that everyone does multiple times per week.”

Many mobile apps, like Yelp and Foursquare, offer information about restaurants, but “we don’t see much of a barrier to entry to doing reviews or social stuff related to restaurants,” Mr. Garrett said. “The real trick is being able to place an accurate order and picking it up, and it being ready and prepared on time.”

Snapfinger presents menus from 28,000 restaurants in 1,600 cities nationwide and in Canada. The service is most popular, the company says, in Orlando, Fla.; Chicago; San Francisco; Portland, Ore.; Houston; and Winnipeg, Manitoba. People can search for restaurants nearby, order and pay from their phones. There are tools for group ordering for an office lunch, ordering favorite items with one click and getting location-based, limited-time coupons.

Image Jim Garrett, the chief of Snapfinger, an online food ordering service. It is free for diners, but it takes a share of each order. Credit... Tami Chappell for The New York Times

Snapfinger is linked to each restaurant’s computerized cash register, and it reflects what is available at what price that day. This real-time information is helpful because each of the hundreds of restaurants in a chain has different prices, daily specials and store hours, and if one runs out of an item, Snapfinger knows it.