Timothy Hewitt, Esquire has a page on how to mod an ibook to 'insert' a bluetooth module. I, for one, am a known fan of Bluetooth.
However, a concern I have is the ability to turn off the Bluetooth Module. I don't mean just stopping people from connecting. I mean stopping power to the BT module in interests of battery life. I'll have to try that out first w/ an external BT module.