Apple finally chimes in with its own iPhone SDK announcement:

Apple today previewed its iPhone 2.0 software, scheduled for release this June, and announced the immediate availability of a beta release of the software to selected developers and enterprise customers. The iPhone 2.0 beta release includes both the iPhone Software Development Kit (SDK) as well as new enterprise features such as support forMicrosoft Exchange ActiveSync to provide secure, over-the-air push email, contacts and calendars as well as remote wipe, and the addition of Cisco IPsec VPN for encrypted access to private corporate networks.

The iPhone SDK provides developers with a rich set of Application Programming Interfaces (APIs) and tools to create innovative applications for iPhone and iPod touch. Starting today, anyone can download the beta iPhone SDK for free and run the iPhone Simulator on their Mac. Apple today also introduced its new iPhone Developer Program, giving developers everything they need to create native applications, and the new App Store, a breakthrough way for developers to wirelessly deliver their applications to iPhone and iPod touch users.

With the iPhone SDK, third party developers will be able to build native applications for the iPhone with a rich set of APIs, including programming interfaces for Core OS, Core Services, Media and Cocoa Touch technologies. The iPhone SDK will allow developers to create amazing applications that leverage the iPhone’s groundbreaking Multi-Touch™ user interface, animation technology, large storage, built-in three-axis accelerometer and geographical location technology to deliver truly innovative mobile applications.

Apple has licensed Exchange ActiveSync from Microsoft and is building it right into the iPhone, so that iPhone will connect out-of-the-box to Microsoft Exchange Servers 2003 and 2007 for secure over-the-air push email, contacts, calendars and global address lists. Built-in Exchange ActiveSync support also enables security features such as remote wipe, password policies and auto-discovery.

I'll need some time to really dig into this, but Apple's announcement represents a near-best-case scenario. Long story short: This is huge. My only niggling off-the-cuff issues are that you need a Mac to develop iPhone applications (which makes sense; the SDK is based on Carbon and OS X) and that the beta version of iPhone 2.0 isn't more broadly available. No matter. There is going to be a deluge of iPhone applications. Suddenly, the iPhone is a much bigger deal than the Mac, and possibly even a bigger deal than the iPod.

Related: iPhone Dev Center