I've created a business that tries to do this before. Well, the business was an events aggregator in NYC, but we envisioned that would be one of the future features.

When you learn how to force people to check-in to a club and broadcast it, you'll have this app. Until then, it's really difficult.

I once had an idea was that you would open up the app and it would have two buttons: (1) MALE (2) FEMALE. Clicking one would check you into that club. This would solve what a lot of people want -- where are the people & who are those people?

Even something that simple though -- what's the reward for the user checking in? On Foursquare, it was awards and badges and stuff. If you could do that around night-life, you might have something.