I have an iPod Touch and it's really cool. It looks a lot like an iPhone. The iPod Touch can be hacked to run most of the iPhone applications and they're basically the same gizmo. The article goes over how to take the iTouch to the next level, to make phone calls. Since the iTouch doesn't have a microphone it requires adding one. Since the iTouch doesn't have cellphone hardware, and it does have wifi hardware, the hack requires using a VOIP client to run over a wifi connection.