Google recently unveiled a non-browser-extension-based method of managing your Gmail account when you're offline.
Up until now, Gmail users who wanted to compose and manage messages without being connected have had to rely on Google Gears. The new method (demonstrated in the above video) accomplishes the same functionality with native HTML5 database and app cache features.
The advantage here is that, rather than the need for creating a bunch of browser/OS-specific extensions, the entire offline process can be managed in a way that's compatible with most Webkit-based smartphone browsers. That includes not only the iPhone, but the Android (natch!) and even the Palm Pre.
It also could lead the way for a flood of feature-rich, platform-independent apps that could make more smart phones at least viable players in the iPhone vs. Everybody Else war.