Guilty!
I caught my former wife cheating by monitoring phone conversations. It's no secret though. I'm publishing the whole sordid story right here on Medium for the world to see.
https://medium.com/@estwald/another-somebody-done-somebody-wrong-song-b3ba2b7cd2f3
I would not keep it secret. My current wife knew all about it right from the start.
I would do it again under similar circumstances, although similar circumstances are unlikely to arise.