that I'm too lazy (and in the wrong industry) to implement:
Frequent visitors to the casino are given a card that they stick into whatever machine they're playing to track their gaming patterns. The casino gives them extra chances to win things in exchange for this data.
Why not do the same thing at the gym? You've already got a card you use to get in, so why not put a magnetic strip on it and network the machines so they record your workouts. Members get weekly emails on their progress, reminders to come workout, etc. The gym can upsell consulting services that are sort of a transitional product between full on personal training and just letting you come in whenever you want.
Obviously, the workout machine people would be the big beneficiaries here, since they'd sell a lot of new equipment, but I bet a lot of their machines could be retrofitted.
NordicTrack, I give you permission to make this happen.
(of course, it wouldn't surprise me at all if this were already out there somewhere)