I have been looking in to communication apps and found that you can actually turn your iPod Touch in to a Mobile phone: you can make calls - send text messages and that is primarily because of 3rd party apps which enable this functioning.
Lately Vopium has released its app for iPod Touch which enables you to make calls (initially FREE and then you can buy from their low cost international call offering) and send SMS. You simply have to visit get.vopium.com from your iPod or download Vopium to your PC or Mac from iTunes.
Vopium is a free application installed on your iPod Touch (2nd generation) allowing you to turn it into a mobile phone. When your iPod is connected to WiFi, you can make calls and send text messages over the internet using your normal mobile number. You do not pay any charges to your mobile operator. You only pay Vopium’s low international call rates. You can obviously also use your iPod to make national calls. Just remember that you need to acquire a Microphone adapter to make calls.