I would suggest taking a look at the source code for Bluetooth protocol stacks for Linux just to get an idea of what you are up against. It may be like with IrDA where you can implement a subset of the stack protocols to get some meaningful functionality, but to implement a stack that is conforming in all areas may not be realizable with an 8051 derivative. This, of course, depends on how much of the stack is implemented in the modules themselves. I am not speaking from a position of authority here, since I have not had to implement Bluetooth (yet).