I have a specific scenario in mind, but I will ask this generally:
Is there a way to make my mobile phone trigger an action on my computer? I am thinkin
Salling Clicker works on the Mac to do just that. I think there is a PC version.
It's a cool tool either way!!!
Edit: Actually, the way your car's handsfree kit and GPS and all that show the number and caller on an incoming call is by implementing the Bluetooth handsfree protocol. If you make the PC look like a Bluetooth car kit (you'll probably have to write the protocol yourself) you could do it.
Failing that, you could write an app for the phone which detects the phone state and sends messages via bluetooth to the PC and then write another custom app for the PC which handles those events. Personally I'd just download the clicker and run with it :)
Edit2: I wasn't thinking of the clicker at all, but it should do what you want. There is a tool called BluePhone for the Mac which does what you want. I'm not sure there's a PC version of it, but there is very likely a PC equivalent if you poke about on the interwebs.