Check out this Video
Right now there are some other good applications like TruPhone which I use works with the 3G network already.
There was a restricting the iPhone SDK on making phone calls using the 3G earlier, but with the release of version 3.2, this was removed and opened up the option to use 3G for phone calls.
Now we see companies and developers showing more interest with the launch of iPad.
I wish if iPhone opens up support to multitasking or at least have an option to run a few programs in the background, which is the only thing that I am missing in my iPhone 3G S
Update : April 4, 2011, 3:56 am
With iPad 2 now you can do video chatting as it has two cameras. Have you tried it ?