Foursquare has introduced a new version of its iOS app that includes a feature that informs users when they’re near to a location that they’ve previously expressed an interest in.

Radar allows users to subscribe to lists – such as TimeOut’s 101 Best Dishes of 2011 – or to add places to their to-do list, and then informs them when they’re near to those locations. According to a Foursquare blog post, another element to Radar is that it will let users know when their Foursquare friends are nearby, so they can meet up.

The Radar element works in the background, notifying users even when they’re not running the app, and uses Foursquare’s Explore algorithm to generate the alerts.

The technology represents an attempt by Foursquare to extend its range of services beyond the check-in functionality that formed the basis of its early success.