Pre-orders and previews begin April 10, launches April 24.
iPhone Application Example: OneTrip
OneTrip is an iPhone-optimized web application (a simple shopping list). Since third-party apps won't be available on iPhone for a while, I thought I'd create a website you could load in Safari on iPhone to approximate having a custom widget.
With Apple's announcements that web-based/AJAX applications are the only way to develop on the iPhone, this example application has been making the rounds.