Good demo, by the way, though I might suggest:
* making it more obvious that it's a CSS-only solution (which is a very good thing)
* showing how to add them - i.e. you just include a CSS file and add a class to the label
* show which browsers are supported, including touchscreens
And possibly a feature request: can you animate as an event? For example, I might want to draw attention to a radio element without checking it.