Believe it or not, it's a piece of cake, just think about it.... iPod Touch can be used as a phone.

[Ionela, from Your Electronics Open Source]
I never handled an iPod touch until a few days a ago. But a friend of mine received as birthday present the media player iPod Touch and so I had the chance to analyze it. What can I say? It's very thin and surprising. Once you start using it, you can not leave it! The iPod touch has a reduced size: height 110mm, width 61.8mm and only 8 mm thick. Weighs only 120 grams. The 3.5 inches widescreen format display has a resolution of 480 x 320 pixels at 163 ppi. The iPod touch provides Wi-Fi wireless connectivity (802.11b/g) - the only iPod to have it.