Some of the software that the early iPhone hackers developed, such as the virtual guitar and games that use the accelerometer, illustrates the potential of the SDK. The entrepreneur and iPhone expert Christopher Allen, for instance, envisions writing software that could filter calls or text messages depending on the position of the phone: laying the phone flat on your desk might indicate that you want to accept only work-related calls. (See "The iPhone's Untapped Potential.")
Nonetheless, says Allen, it's still not a complete free-for-all. It's not clear whether programmers will have access to certain layers of information about the phone, such as those that could allow them to build Bluetooth peripherals like keyboards. Allen says that he hasn't yet had a chance to dive deeply into the SDK, but he's not sure whether it will allow for software that lets iPhone users receive data, such as instant messages, while they're placing calls over the cellular network (something that's not possible now).
Already, Apple has enlisted some major companies to develop early applications that will give the public a taste of what the development kit allows. At the press event, AOL unveiled its iPhone-compatible instant-messaging program, and the game company Electronic Arts showed off Spore, a game that uses the accelerometer to control play.
While the SDK is downloadable right now, third-party programs written for the phone won't be available until June, when Apple releases the iPhone 2.0 update. At that time, people will be able to download programs via iTunes, in the same way that they download songs and movies. Allen suspects that, as it has with podcasts, Apple will promote the programs that are the most popular, "which means the quality stuff wins," he says. "That's definitely not what's happening in the cell-phone world right now: quality is not there." Of Apple opening the iPhone, Allen says, "I think this is a pivotal thing."