As the founder of Thrillist, a New York City media company that prides itself on being an arbiter of all things cool, Ben Lerer knew his business needed to get into the newest "it" space -- mobile apps. Thrillist's core business consists of sending 2.5 million subscribers daily e-mails that highlight new bars, restaurants, and shops in 18 cities. An app, Lerer thought, would be a logical extension for the business. "We want to create as many opportunities as possible for our guys to interact with Thrillist," he says.

The initial question, as it is for most businesses, was, What to include? An ideal app would engage Thrillist subscribers when they were away from their computers and attract some new users as well. Lerer and the developers he hired also recognized that to stand out, the app would have to do more than solely reprint the daily e-mails in app form. "That would have been way too vanilla," says Jesse Boyes, who oversaw the four-person team that worked on Thrillist's app. "We were looking to strike a balance of it being half-utilitarian and half-entertaining."

Lerer and his associates brainstormed possibilities for a few days. One idea was to design an entertaining app modeled after the Choose Your Own Adventure genre of books; the app would curate a night on the town based on selections a user made on the app. For example, the app might instruct a user to enter a nearby bar and then choose between real-life actions like ordering a drink or approaching a single woman; based on the selection, more options would appear. But it became clear rather quickly that though the app may have been amusing, it lacked a level of utility that Lerer sought.

Lerer and Boyes shifted their attention to one of the most popular features on the iPhone: its built-in geolocating capability, which allows iPhone users to easily pinpoint their location on a map and allows apps to give users information based on their location. The group spent some time studying the mobile apps of other review sites, such as Yelp and Citysearch, both of whose apps were designed to capitalize on location. What it found was not surprising: Those sites contain reviews of all kinds of businesses, and their apps generally displayed just about all businesses near a given location on a map.

Thrillist, on the other hand, differentiates itself by spotlighting only businesses of which it approves -- about 150 a week across its markets. Its database had about 13,000 recommended businesses. Was that enough to power a useful app, Lerer wondered? He was tempted by the idea of having his editorial team write even more reviews to provide the breadth seen in other review apps. But it didn't take long to recognize that aggregating as many reviews as possible would pull Thrillist away from its core business. "Our strength is curating and filtering for a certain type of person," Lerer says. "We decided we didn't want to get into the game of creating new content specifically for the app. That focused us."

Lerer and Boyes decided that the app would focus on displaying Thrillist-approved businesses on a city map. The app, which cost about $50,000 to develop, debuted in June. Over the next four months, it registered about 160,000 downloads. Open the app, and a map appears with icons representing bars, restaurants, and retailers. Tap an icon, and up comes a review accompanied by a photo and, in some cases, video. Click on tabs labeled Eat, Drink, Shop, and More to search specific categories. The touchscreen allows users to easily scroll to different parts of the city to view more businesses. The app also includes a few nonmap components, such as an index of recent reviews and a tab that marks a Thrillist subscriber's favorite establishments.

Just like the website, the app is constantly updated to reflect the latest reviews. An app designed for Android devices was set for release in November, and one for the iPad is also in the works; that software will focus on letting users organize and share reviews. Why the difference? "The iPad is not as much about location," Lerer says. "It's more about hanging out and browsing."