iPhone: Social location-tracking app Foursquare released a new update today for the iPhone, adding a new feature called Radar. Radar pays attention to what you're following on Foursquare and alerts you when you're near any followed location.
For example, if you're following a Top 10 Dessert Restaurant list and happen to be near one of the restaurants, you'll receive a notification from Foursquare to remind you to check it out. This update seems to require iOS 5, so be sure to upgrade and get yourself set up first.
Note: The update to the Foursquare app may not be available to everyone right this second, so be patient and it should show up for you at some point later today.