I want to buy an iPod touch, an external microphone (nonheadphones, I am in the army and can't wear them at work), and a software application that allows me to make voice calls over the Internet. I am around free wifi constantly and want to use the the ipod as a phone, basically. What iPod gen and iPhone OS, microphone, and applications work best together?

I have read alot of reviews but I can't find anything that really works, and if it does, it sucks. Any suggestions?

I think this will work: iPod Touch 2nd gen, iPhone OS 2.2, iVoiceIII microphone & Macally iPod Speakers IP-A111, and the Truephone app.