Snap! ties your telephone to social networking sites. It will notify you whenever people with the same interests as you are in your neighborhood. You can then exchange contact information with these people automatically and wirelessly. You can use snap instead of your standard contact list - it uses a p2p network to keep your contact list up to date at all times.
Check out the screencast on http://www.snap-project.net
on the main page if you are interested.
Any comments are appreciated. Both the site and the program are still work in progress