Did somebody say "web apps are dead?"
It sure wasn't Google, who — still smarting from their app being unceremoniously yanked from iTunes — have figured out how to sneak the same functionality into the web-app version.
Turns out if you run Wave within the Safari browser (image credit Engadget), you have the option of a borderless "app mode" that removes Safari's buttons and user-interface controls. By quashing the Safari UI, Wave can occupy every available pixel of the iPhone's screen real estate. And thanks to code that's optimized to a variety of browsers both mobile and desktop (including Android and Chrome), Wave's performance is crisp and quick.
Google Wave is currently only available in the USA, and you'll need to request an invitation from Google first.