I think it would be interesting to use Bluetooth to automatically exchange business cards with nearby people (e.g., at a conference) to determine whom you might want to talk to.

Bluetooth is surprisingly difficult to get working between different phones. When phones actually do recognize each other it takes a long time to pair. Once pairing is completed (even between iPhones this takes ~45 when it works) transfers speeds are fast. Communicating with our server in the cloud is a compromise, but it eliminates the cross-platform compatability and pairing problems of Bluetooth.

As someone else noted, you're still waiting around for ~25 seconds with Bump. That's an incremental improvement and users may be slightly more forgiving of the time.

Have you looked into Bonjour?