Adding bluetooth to my navigation system

Hi,

Whilst sorting out my DVD issue, I was also thinking of getting an in
car phone system. Although the navigation system has a phone option,
I don't believe the previous owners bought that extra when they bought
the car.

Is there something I can buy to enable it to connect to my phone via
bluetooth and integrate the dialing, sound etc. through the car
system?

thanks in advance for your help.

Lee.