Include Xenforo Redactor iframe in Tampermonkey

I'm trying to create a Tampermonkey script for a website running Xenforo. Specifically I'm trying to target the WYSIWYG editor iframe and run the script when I edit the content but I just don't know how to do it.

If I target the website itself, the script doesn't run when editing the content in the iframe. The source code doesn't have a src tag, and if I check the Chrome inspector the frame in question is on about:blank

To answer my own question, here's a more detailed explanation on how I got it to work.

In the userscript header, include waitForKeyElements:

// @require https://gist.github.com/raw/2625891/waitForKeyElements.js

Then in the code section:

waitForKeyElements (
    'body',
    r,
    false,
    '.redactor_textCtrl'
);

function r(jNode) {
    'use strict';

    jNode[0].addEventListener('keyup', function(e) {
       console.log(e);
    }, false);
}

This allowed me to act upon changes in the text editor.