From Apple's website:
Can I extend service coverage on my iPhone beyond the warranty?
The AppleCare Protection Plan for iPhone will be available in July. The AppleCare Protection Plan for iPhone will extend the hardware repair coverage to up to two years from the original purchase date of the iPhone. The AppleCare Protection Plan for iPhone must be purchased while the iPhone is covered under Apple's One-Year Limited Warranty for iPhone.
http://www.apple.com/support/iphone/service/faq/#faq10