Try to install bt plugin to see if the problem lies with MM, your bt device or with OS2008 system.
There is a number of types of bt devices.
Some or most of them require pairing but you can connect bt gps alone devices without pairing ( or some I have already tested).
I am writing bt applications and full communication (two-way) protocol is really complicated requiring each bt device to respond with some status and bt type data (pairing on or off).
Bt plugin should solve your problem as you can make a selection of a type of bt device you are going to connect to.

I am just writing a nice gps navigation appplication based on 2 gps units.

Darius