The iPhone Bluetooth Project has been quietly pining away at the Bluetooth aspect of the iPhone for months. They recently released BlueSn0w, a small tool (which bears a striking resemblance in name to another recently released - but unrelated - tool) which is mostly proof of concept. It work strictly via command line, but they promise updates in the near future. This could lead to some exciting things, like Bluetooth file exchange being enabled, among other things.
Our team has successfully been able to demonstrate a 'pwnage' of the bluetooth chipset allowing anyone to write/implement a fully functional Bluetooth Stack that runs on your iPhone, and this will be our next step.
I've attached the tool and their Readme to this post - if you're the command line type, give it a whirl. A few things to note: in this early release, WiFi /must/ be off on your iPhone when running this, and the device you're trying to find should be set to Discoverable.