Alexis Rondeau developed Unblah, a free "meeting-buddy" app to help people who tend to talk to much during online meetings. It's basically a speech-triggered timer with "traffic light" notifications to help you control yourself. You can also watch a live timeline to get a sense of your verboseness as the meeting progresses. Demo video below. Of course, the first step is admitting you have a problem (and downloading the app).
From the FAQ:
I have this person on my team who talks WAY too much and never notices it. They LOVE hearing themselves talk and never shut up. Should I tell them to get this app?
First off: I believe your struggle with this person is 100% real. I fully believe their behavior is affecting you negatively.
But, my answer is a STRONG NO. Please don't use Unblah as a proxy for a difficult conversation that sounds like it needs to be had.
Think about it: They would never use it anyways, because, as you're saying yourself "…and never even notice it.".