The FourSquare API seems to be very user-centric: After logging in via OAuth I can see my friends check in, and which of my friends are currently checked into a given venue.
I'm looking for something more venue-centric, where I can get a list of everybody currently checked into a venue (friends and non-friends), or ideally receive a notification each time there is a new check-in at a specific venue. Is this possible with the existing V2 API?
I know you asked this 2 months ago and surely found an answer already but to answer your question directly.
where I can get a list of everybody currently checked into a venue (friends and non-friends)
The FourSquare version 2 API has a venues endpoint
https://foursquare.com/dev/merchant/index_docs.html
A sample call will give you a stats field in the response
https://api.foursquare.com/v2/venues/5104
Stats: Contains checkinsCount (total checkins ever here) and usersCount (total users who have ever checked in here).
for more venue information, FourSuare has a subset to the version 2 API called the venues project with more venue driven data you can update and mine through.
You can check the venue checkins and mayors, comments, etc. Easily with the foursquare API, just check the API documentation for which calls can you make.
I wrote a handy article about how to connect to the foursquare api and make calls to it through PHP, you can find it here http://ryokuweil.wordpress.com/2011/08/29/how-to-use-the-foursquare-api-v2-with-oauth-and-php/
Authenticated calls /venues/herenow will return a list of people currently checked in. See https://developer.foursquare.com/docs/venues/herenow.html
To receive notifications when new users check-in to a venue, you need to have your application authorized by a manager of the foursquare venue, then enable your app (on foursquare.com/oauth) for the foursquare Venue Push API
来源：https://stackoverflow.com/questions/7369934/how-can-i-watch-a-foursquare-venue-for-check-ins