Personally I use bluetooth to provide a radio link between various computers, carrying the Delay Tolerant Networking research group's Bundling Protocol (see RFC5050). The devices automagically detect each other and forward traffic towards its ultimate destination. The end to end path might include conveyance over Bluetooth, TCP/IP, AX.25 links using amateur radio equipment, and other assorted methods.

So, bluetooth is, in general, just another radio that you can do anything you like with.

All that I've mentioned I can currently do on my N800, and I expect my N900 will do it too, although the USB host issues might cramp my style a bit.

Hopefully I've broadened your horizons a little.