Apple unveiled the iPhone Application List and boasted that it sold one million of the new 3G (third generation) devices in the product’s first weekend on the market. More important than the sales figures is the coup that Apple has pulled off: The iPhone 3G looks to be the first mobile device to make the leap from telecommunications to data. That makes it the first mobile platform to merit serious attention from marketers.

The iPhone inspires a passion among its users that few technology products have ever achieved. Ask an iPhone user to tell you what he or she likes and you’ll get a 20-minute sermon, complete with demos. What strikes me is that most people tell me they use the iPhone more for data than for telephony. This is where the product is a game-changer.

The mobile Internet has been an unholy mess for several years. Each handset maker, network operator and service provider uses a slightly different technology. This pointless incompatibility has frustrated application developers so much that many have decided simply to wait out the market until consensus is reached. About the only standard anyone has been able to agree upon is Mobile Web, a hobbled subset of the World Wide Web standards that doesn’t do anything particularly well.

Apple is bidding to change all that. The two big innovations in the iPhone are a usable http Web browser and sufficient local memory and storage to run applications on the device. This second feature is critical. Few people will choose to interact with their iPhone primarily through the browser, although they will browse to retrieve information. The beauty of native applications is that they can take full advantage of the iPhone’s speed and interface. When combined with a robust Internet back end, some truly interesting uses will develop.

In industry lingo, this setup is called client/server. Millions of people already take advantage of a mobile client/server architecture every day when they use their BlackBerries from Research in Motion. The BlackBerry’s e-mail interface is second to none, but an equally important usability factor is the device’s rapid performance. That’s because the BlackBerry downloads messages continually and displays them locally for rapid access. If the Blackberry’s performance was as slow as a Web e-mail program like Yahoo! Mail or Gmail, I suspect few people would bother with it.

Apple’s applications initiative is meant to give developers the means to build client/server applications on the iPhone. This can give users a fast, pleasant experience that’s optimized for the platform. Mobile Web doesn’t come close.

With an impressive list of more than 500 out-of-the-box iPhone applications and the capacity for developers to create really functional client/server programs, the iPhone stands to be the first truly mobile data device.

No cell phone maker I’ve seen has yet produced a meaningful competitor. Their origins are in voice, and most still don’t get the data thing. Apple’s early lead with mobile applications makes it the front runner in his new field.

Here’s the opportunity for marketers. Facebook pioneered the idea of using applications as a means to sell products, but there are so many Facebook applications right now that it’s almost impossible to break through the noise. The iPhone is currently an open field, and since people spend a lot more time away from their computers than in front of them, there’s more potential for audience engagement. The audience may be smaller, but the prospect of getting them to actually use your service is greater.

The applications that succeed on a mobile device will undoubtedly be different than those that work on a social network. Location awareness will be critical. Think in terms of what people want to do and know when they’re standing on a street corner or waiting in an airport. Give them services that help pass the time or entertain them. Better move quickly, though. I suspect the iPhone Application List won’t be a short one for very much longer.