4. Social Radar

play.google.com
itunes.apple.com

With this app, you can find out who is near you and which of your friends are attending local events. Have you just found a new group of people online? Find out if they are near you or at the same event as you. Get alerts if people you may know, or people you would like to know, are nearby. You can even get reminders of their details so you have a few ideas around what to talk about.