You can apply these animations to any :checked element in your page, just, by default, these are designed and meant for radios. I see it difficult to make flash or boing an input field while you focus or check it, don't you think?
Just so you know, on the Checkbox page, the animation for "Splash" can be triggered without actually changing the checkbox state, by clicking just below the checkbox. I guess the hit area for the animation is bigger than the checkbox.