Show/hide div if “other” radio OR checkbox is checked with Formtastic
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This is a lot like other questions that have been asked. I know how to do this with HTML/Javascript, but my question specific to Formtastic.

(Here is a link to almost the same exact question, except all I need is to figure out how to get Formtastic to emit the HTML similar to the example here: http://stackoverflow.com/questions/6125738/show-hide-div-if-other-radio-or-checkbox-is-checked)

Often you'll have a list of radio buttons:

 - Choice 1
 - Choice 2
 - Choice 3

Well, that is all fine and dandy, and Formtastic handles it with ease. But then what happens when I want this:

 - Choice 1
 - Choice 2
 - Choice 3
 - Other:         [ text input here]

The text input should be greyed until I click "Other." If I choose "Other" I need the user to type in what it is. (And the same argument would apply with checkboxes as well.)

I realize the interactivity is Javascript, and not Formtastic's job as far as that goes. What I'm talking about is the actual markup.

Is there a way to make Formtastic emit this?