I don't think it needs something deeply clever involving hardware breakpoints, sniffing for virtual pages backed by real memory or something like that. And probably that's why it is described as a honeypot.

It can just be something exposing a data structure that gives the player some unfair advantage and them watching the players that could only have achieved some very unlikely advantage in the game by exploiting this information.

In a FPS for example, if a player consistently anticipates their adversaries sneaking behind a wall, well beyond what would be dictated by probability laws, there's a very high chance that he is cheating in a way that allows him to "see" their adversaries behind walls.