Bluetooth connect to GPS for phone

[eenieMINI]

I have an HPrx5915 that has the TOMTOM software on it and has bluetooth. It advertises data capability with phone. What I am wanting to do is use it as speaker phone in the car. Connect the Treo to the HP via BT and let the HP answer the phone, use the contact list, microphone, speaker etc becuase I can hook the HP to the stereo. I was thinking instead of investing in a Parrot system I might coud do this as most of the newer GPS units are used as handsfree phone.

So I make the BT connection but the only service the Treo is offering is serial port. Does the treo not support handsfree with gps units??.. I'd hate to go out and get a separate handsfree system as a solution and still have it not work. At the moment I use a BT earpeice just fine but wanted the speaker system.

Any ideas or insight appreciated.