"Poiesis is King of the elliptical trainer!" "Achievement unlocked: 200 pound club" "New badge: Power Hour" "Most consecutive workout days: Poesis (42)"
Add an iPhone app maybe for cardio workout tracking that's harder to cheat.
This would be totally awesome. Maybe stick a leaderboard up on one of the big screens. Only problem is that it would encourage people to visit the gym, which is a bit of a problem for the current business model. You might have to switch to pay per use. Or maybe charge extra for the frequent users? But then there's a monetary barrier to working out.
I have to ruefully say that if it weren't for the fact that this actually actively contradicts the current business model, it's a great idea.
It'd at least do well for retention I'd wager.