iPodTouch as a VoIP client?

The iPodTouch's format made me immediately wonder how much of its core was shared with the iPhone. engadget noticed that some of Apple's press showed the iPod with a BlueTooth icon and there is a BlueTooth chip confirmed within it, but disabled. Assuming a bit of hackery, the WiFi enablement and a BlueTooth headset I wonder how long until somebody makes VoIP phone out of their new iPod. I wonder if Apple's exclusive deal with AT&T precludes Apple doing an iPod VoIP deal?