Today, the company is starting a gradual roll out of a new version of the Foursquare app for Android that marks its biggest move into a “post-check-in” experience yet: A feature that will ping phones with personalized recommendations based on a user’s targeted physical location, without needing them to check in at all.
So, if you walk into a restaurant you might get information on what's good. If you want into a bar you might get a deal (but don't expect much of that). The new version is rolling out slowly first to Android, and later to iOS. And, no, it doesn't drain your battery too much. I'm still not interested.
See also: Foursquare Blog