That's a cool idea. Accelerometer support for JS was added to iOS 4.2 [1], so it should be possible to modify the CSS transformations based on the DeviceOrientation [2].
It looks like the C7 is running an older version of WebKit that doesn't support CSS transitions. It seems to be running v525/3.0 [1] and it looks like transitions were only in nightlies at that point. [2]
http://snook.ca/archives/html_and_css/css-text-rotation