Foursquare has sent its 4.0 version of its iPhone app live, complete with a new iOS 5 function called Foursquare Radar.

The new app allows you to take advantage of the region monitoring found in iOS 5, and subsequently sends you notifications of places nearby that you keep in lists. Think of them as sort of reminders to check in at your locals.

Say you have multiple friends checked in somewhere, more than three to be exact, then Foursquare Radar will push a notification to your iPhone letting you know. 

You do need to opt in to Radar in order to take advantage of the function, useful for those who don't want their location being known too often, but then again why would you be using Foursquare?

As of now Foursquare Radar doesn't exist on any platform other than iOS, it is, however, being developed for other mobile operating systems. 

You are going to need to get your handset updated to iOS 5 in order to get things working, not hugely easy at the moment as Apple's servers are a bit overloaded. It is starting to calm down, as Pocket-lint discovered this morning when our devices started to update. 

This is the first app to take advantage of new functions in iOS 5. Who knows what's next... 

Do people still use Foursquare? Let us know in the comments below ...