Wow, that's cool. I'm going to give it a try. I don't know what happened to Thanks button, I don't see one anymore, but thanks! kkI make phone calls with my iPad using Whistle Phone. It's free for USA but you have to listen to a short ad before call is made (like 10 or 15 seconds). Incoming calls do not get the ad of course. But it works rather well. I would assume skype would too, as well as TextFree Voice, Second Line, etc.
When my iPhone is going to be down for a while such as during a restore process and re-jailbreak, and I am not near an easy-to-forward-to landline, I have my iPhone calls forwarded to my Whistle Phone number and take calls with iPad. The iPad will work with the iphone-compatible headsets. Or I just use it as a speakerphone on the iPad, sans headset.