Apple hinted that the iPhone might become more useful to business workers during a discussion hosted by Morgan Stanley on Wednesday.

"Tomorrow we're going to talk a bit about the iPhone in the enterprise at our event on campus," said Peter Oppenheimer, chief financial officer of Apple, via a webcast of the Morgan Stanley Technology Conference. "We believe the iPhone is great for all parts of the market, including the enterprise."

Apple has scheduled an event on Thursday for developers, during which it will talk about the software road map of the iPhone, including details about the software development kit for the device and enterprise use, he said. The SDK will allow developers to create applications for the iPhone. Since Apple launched the iPhone last year, it has been closed to third-party developers.

In addition to opening up the iPhone to developers, he suggested that other changes may be on the horizon. While the company has created revenue-sharing agreements with operators so that Apple earns ongoing revenue as users pay for their mobile subscriptions, that model may not apply everywhere into the future, Oppenheimer said. "We're off to a great start, but we're learning and we're not wedded to any one particular way to go to market," he said. "Our objective is to drive scale and take market share."

This year, Apple expects to offer the iPhone in additional European countries and enter markets in Asia, he said.

The company sold 4 million iPhones in the first 200 days that it was on the market, Oppenheimer said. Users of those phones are all over the world, even in countries where Apple isn't selling iPhones. That's an indication of the high demand for iPhones, Oppenheimer said.

Even though Apple ties the iPhone to a particular operator's network, users have discovered ways to unlock the phone so that they can use it on the network of their choosing. "We believe it's occurring at a significant rate, it's just hard to estimate," Oppenheimer said. "We believe the unlocking is occurring because of unprecedented demand for the iPhone. ... We view this as a positive indicator of future demand and interest in the iPhone."

In the fourth quarter of 2007, more iPhones were sold than Windows Mobile devices in the U.S., according to recent research from Canalys. Among smartphones, only Research In Motion's BlackBerry devices sold more than iPhones in the U.S. during the quarter.