Fast-food, eating out, are in the DNA of this country.  Food is everywhere, 24/7, accessible, inexpensive. And now also at your fingertips.

Not a day passes without a new “food” app making the headlines. Gluttony meets GadgetsMania. It’s fun. It’s as fast as it can get,  thanks to store locators and in-app ordering. It’s convenient, even more convenient thanks to special discounts and coupons. Soon, apps will also allow you to pay for your fast-food fix within the app!

-Make it Fun: The PizzaHut case

Craving a pizza? PizzaHut is designed for the mischievous 10 years-old in you. It lets users indulge devilishly in the creation of their dream pizza, and smile at their own excesses, as the Iphone screen displays flying toppings and sauces.  A 20% discount makes you feel even better about your little sin.

Numbers speak for themselves: $1million sales in 3 months.

-Not just the IPhone: the OpenTable case

Online restaurant reservation site, OpenTable, has happily seated 1million diners via its mobile apps. Based on an estimated $50 average check per diner, that’s $50 million in revenue for its restaurant partners.

The OpenTable app allows diners to find and book reservations at more than 11,000 different restaurants in multiple countries. Unlike others, OpenTable is not just for the Iphone: key to its success is a mobile strategy that sees the app seeded throughout the various mobile platform. You can use their mobile site, or download the app on the Android,  BlackBerry, PalmPre, and obviously the Iphone.

-Make them pay through the phone: the Starbucks case.

Still no numbers have been disclosed, but Starbucks is certainly the one to look at closely, since it is paving the way for the fast-food mobile revolution with its recently launched myStarbucks application. The app has a slew of nice designed features to remember your friend’s favorite drinks and locate nearby Starbucks stores.  But what’s interesting is that, if you’re in a few select West Coast areas, you can turn your Iphone in a  a Starbucks card, and pay for coffee using a bar code on a phone’s screen.

-Make it Social: the DunkinDonuts case

The DunkinRun app is the Office dream: the app lets you email or text your friends to tell them when you’re leaving, and give them the option of ordering stuff from Dunkin Donuts. It had never been easier to get a coffee fix. Social meets mobile and mobile meets revenues!