I made something long time ago since I heard the news about accelerometer support in Firefox 3.6.
I use a MacBook and MacBooks has accelerometer built in, so I made this. I call it Typentilt, which comes from from Type and Tilt!
To use it just open it in Firefox 3.6 beta 4 or later, type some text in and then rotate your MacBook vertically. The text you type appears, filling the browser. It’s best to use this in Full Screen! (Cmd+Shift+F in Firefox 3.6)
Download: typentilt.zip