I think it would certainly be doable, you do need a critical mass of users though to make it worthwhile which means you'd also need to write a version in Java so people can run it on their phones.

Otherwise you may as well go the "bonjour" route and limit yourself to tablets or other wifi enabled devices - the Bonjour (zeroconf) and service discovery stuff is all out there. I'm not sure whether it could be directly transplanted to use Bluetooth as the communications medium or if it would be worth going for some simpler scheme.

There are things like instant messenger apps for Bluetooth (e.g. http://www.valhallachat.com/?q=overview with source available too), it's in Java as it needs to run on phones, this may be an issue for us though).

Anyway, sounds interesting. Anyone with more Bluetooth knowledge know if you could do a service discovery (where the service is "job title", "interests", etc.) using Bluetooth?

Simon