There is a simplier and more reliable method
They could do what my did. When we were married 18 years ago, she told me in no uncertain terms what she'd do to me if she found out I'd cheated. I'll spare you the details but "Full Bobbet" and "stir fry" should serve as clues. As a sign of trust, I bought her a set of kitchen knives. I know she'd do it, too.
When my youngest stepson married two years ago, one of the gifts we gave them was a set of knives. I told them the story and concluded, "Jim, you've been warned. Heidi, you've been armed."