can someone tell me if their is an app to use the N900 as a headset like over USB, so my pc will detect it and i can use it as a headset?

OR

An app to use the N900 as a bluetooth doogle over USB, so i can connect a headset to the N900 and use on pc?

OR

Is there an app that lets you use google voice to make phone calls but "without needing your phone connected to a carrier"

In otherwords my phone has no service, but when i have a internet connection is their a google voice app to let me make phone call over that?