Is it possible to show / hide certain form fields on an entry page depending on whether or not, say a checkbox is selected? Hoping for an add-in that can handle this.
Since you're only concerned with showing/hiding fields based on user choice, the Entry Type add-on would do the trick. It is "a dropdown fieldtype that shows/hides other fields on the publish page" based on the chosen option.
I'm not sure that it's similar enough to those to be a duplicate, as they specifically sought to change other fields values, or show/hide fields based on entry ID, but the same technique is used.
<script/> tag, you can use jQuery to show/hide the other field based on the value of the checkbox field and an onchange event.