Foursquare has just released a major update to its iOS app for the popular location-based social network introducing a new iOS 5 feature, foursquare Radar. Designed to work in tandem with the enhanced location features of iOS 5, foursquare Radar allows users to receive notifications about interesting and cool things happening nearby. The features leverages information in the user’s Foursquare profile such as lists they’re following, to-do…