Michael Schneider, an attorney in the Seattle office of Wilson Sonsini Goodrich & Rosati, spends his off hours tinkering with applications for the iPhone. The amateur programmer’s first effort, a 99-cent application called Direct Line, let iPhone users skip automated phone systems at companies to connect with live customer support.

That first application, since bumped to $1.99, got immediate traction, and Schneider followed with three others. Today, his applications have been downloaded 100,000 times at Apple’s iPhone App Store — and he rakes in 70 percent of the sales.

“It is a new frontier,” Schneider said.

More than individual enthusiasts like Schneider are jumping on the iPhone bandwagon.

Seattle-area companies ranging from web startups to tech giants Amazon.com and Microsoft are coming out with a growing array of iPhone applications, looking to tap into the sleek device’s tech-savvy user base to drive business. Game companies such as RealNetworks, PopCap and Big Fish Games also are moving onto the platform.

[See list of iPhone applications from Seattle-area people and companies.]

But while many iPhone apps are generating serious buzz, their ultimate effect remains unclear. IPhone users, though growing in number, remain a small part of the overall mobile market. For a mobile-phone application to achieve broad success, it will have to work across multiple platforms, analysts say.

It’s not hard to see why many are drawn to the Apple App Store, the website featuring an array of downloadable iPhone applications. Any developer can submit an application for consideration, and, if accepted, he or she can benefit from Apple’s marketing machine and distribution system.

Already, some of Seattle’s young web companies have found instant success on the iPhone. Restaurant review website Urbanspoon, for example, came out with a free application that lets people shake their iPhone to get a listing of nearby restaurants (it uses the iPhone’s GPS software); it’s been downloaded 2.2 million times.

BigOven, another startup, put out a free iPhone application that allows people to search through thousands of recipes. So far, it’s topped 1 million downloads. And the iPhone is winning support from the developer crowd; an informal group of iPhone enthusiasts formed a new club in Seattle last month to brainstorm ideas and create new applications.

The iPhone and Apple App Store have “created a thriving ecosystem with an effective reach that dwarfs any other path available via a single platform,” said Jeff Holden, CEO of Seattle web startup Pelago, which works primarily with the iPhone. Pelago has a mobile application called Whrrl that lets people track friends and their activities.

Increasingly, big tech companies are eyeing the iPhone. Amazon.com early this month released its own iPhone application that lets users browse and shop on its retail sites. The company included an experimental feature that lets people snap a picture of a product, which Amazon then attempts to match with items for sale on its websites.

Even Microsoft, whose Windows Mobile operating system is used by many iPhone competitors, has jumped into the game. The software giant, through its Live Labs unit, released its first iPhone application this month. Called Seadragon Mobile, it lets people zoom in, out and around super high-resolution images.

As larger, established companies start playing in the Apple App Store, smaller developers wonder if the scrappy, bootstrap nature of the iPhone ecosystem is changing.

“I believe the biggest challenge is that no one knows how the economics of iPhone development are going to play out,” said Peter Boctor, an independent software developer who created Hot Popcorn, an iPhone movie review application with built-in ticket purchasing.

The big question marks are whether large companies will crowd out the small developers, how users will sift through the expanding number of iPhone applications, and whether application prices (many are free) will trend upward or downward, Boctor said.

Nic Covey, director of insights for the telecom practice at the Nielsen Co. market research firm, said he is impressed with Amazon.com’s new iPhone shopping application, saying it “really has the potential to be a revenue generating tool” for the company.

“This idea of taking a picture of things and getting info on that really elevates the value of mobile commerce,” Covey said, adding that it will give Amazon another way to peel customers away from traditional brick-and-mortar retailers.

But Covey pointed to the iPhone’s relatively small user base — just 1.5 percent of the 224 million U.S. mobile subscribers at the end of September — and said for Amazon or any other company to achieve real traction with mobile phone users, it will have to expand to other platforms.

“There are millions of mobile data users that aren’t using the iPhone,” he said.

Schneider, the attorney from Wilson Sonsini, is clearly in the iPhone camp. A heavy iPhone user, he said his phone sometimes reaches the maximum capacity of 142 applications.

“I’ve gotten to the point where I have started deleting,” he said.

Todd Bishop contributed to this report.