Is there any app that allows free phone calls with iPad?

Skype..

I have had flash running successfully on various android phones that I have owned..
A google voice number and talkatone.

Whistle
The video shows an iPad calling another iPad as an example.
http://www.youtube.com/watch?v=v3AKROpBfAs

I use talkatone, which is connected to my google voice. I can call any landline or mobile for free on my ipad 2.

i have whistle
works fine, just listen to a commercial first

Whistle not working for me. Just get a red dot at the top of my ipad and nothing. I went right next to my wifi router and still nothing.