I find it so useful and easy to add to a Moodle site - and it is free. It is great for developers who just want to occasionally test out some basic accessibility on their development site but it can also be useful in production. Best of all, it is super easy to turn on and off.
To get started, go to https://userway.org and click on the Get The Widget button. You'll need to sign-up, but like I said, it is free and I haven't received any junk mail since I signed-up.
At the end of the process, you get an HTML snippet that you can then just go and paste into the Within HEAD section of the Moodle Additional HTML page. It will look something like this (but with a different account code of course):
Although they ask you for the website URL, I noticed the snippet works on any website as long as you have a valid account id. I think they just want to know on which sites their service is on.
When doing development, I find that using UserWay provides some useful insight as to what a user might be experiencing.
Initial Accessibility Lesson After Installing UserWay on Your Moodle Site
With your computer speakers/headphone on, click the UserWay Read Page button, close your eyes and start pressing the Tab key on your keyboard. Try to navigate your website and see how long it takes before you get completely lost or confused.
Hope you find it as useful as I do. If you don't like it, just remove the code you added and it will be gone. No plugins required. it is compatible with most websites, not just Moodle!