If the Jason Mercier prop bet extravaganza proves anything, it's that there's just not enough out there for poker players to bet on. They'll take action on anything and everything, including piling more risk onto events they're already betting thousands of dollars on simply by buying in.
A subsection of tournament-based prop betting is "last longers." Poker players betting on who will make it farther in a tournament has a long and rich history. It's not unheard of for players to make last longers that are worth more than the tournament buy-in.
Most of the bets are between two players or among a small group of friends, but last year, Ben Keeline made waves with huge last-longer pools in the World Series of Poker Colossus and Main Event.