Trulia, one of the Web's most visited home listing sites, on Aug. 25 is introducing a tool available on Apple's (AAPL) iPhone that can locate all the listings and open houses in a user's vicinity.

The free software application uses navigation technology to summon data and displays the results on an interactive map. It lets users call up such information as price, photos, square footage, and number of bedrooms. Another tap of the screen sends a call or e-mail directly to the listing agent. "It's all about convenience," says Trulia CEO Pete Flint.

Trulia is also releasing home listing applications for Research In Motion's (RIMM) BlackBerry, Samsung's BlackJack, and Dash Navigation's Dash Express, which provides navigation services using GPS technology. Trulia's service will also be available on various mobile operating systems, and on devices made by Sony Ericsson and Nokia (NOK).

Competitive Playing Field Trulia, which boasts information for 70% to 80% of the properties on the multiple-listing service database of real estate listings, will be the biggest listing site with an iPhone application. But it's hardly alone. FrontDoor.com says it will introduce an iPhone application later this year that not only searches nearby listings, but also integrates video and information about what it's like to live in a given neighborhood.

StreetEasy.com's two-week-old iPhone application, which provides location-based for-sale listing information for New York City, has been downloaded about 5,000 times. The application was designed with New Yorkers in mind, letting surfers see available properties not just in a neighborhood, but also in a given building.

Coming versions of StreetEasy's iPhone software will make it possible to search for open house and broadcast observations about specific buildings. "People are experiencing real estate by walking down the street; they're not experiencing it in front of the computer," says Dawn Doherty, StreetEasy's vice-president of business development. "It takes people involved in searches one step closer to the tangible product."

Greg Swann, a broker for BloodhoundRealty.com in Phoenix, says that while the Trulia application may undermine the role of buyers' agents, it will probably be a boon to sellers' agents and customers. He's quick to add that as empowering as the iPhone apps may be for buyers, they can't replace the advice and negotiating abilities of a good Realtor. "Anyone can change their own oil," Swann says. "But then why is there always a line for Jiffy Lube?"