Yes, that is correct. you can use an iPod or MP3 player to make VoIP calls.
How is this possible, you may ask?

Just keep this one fact in mind...when connected to a PC, an iPod or an MP3 player is recognized as an external drive. You can store more on the "drive" than just music or video.
With that in mind, here's what your player needs to make VoIP calls possible:
1) Enough disk space to hold a VoIP softphone program such as Skype, GoogleTalk or MSN. A softphone is a software version of a VoIP client. Essentially, a softphone uses the power of the PC as a replacement for hardware such as a phone or telephone adaptor box. Remember that adaptor that Vonage sent you?
2) A microphone on your iPod MP3 player. Since most players now offer a voice recorder function, this is a given.
3) A Softphone client like those mentioned above. Skype is the big kahuna here. They have millions of installed users worldwide. GoogleTalk is gaining on them fast, though. Don't forget, calls between users of these clients is free. So, if you have Skype and call another Skype customer, the call is free.
If you need to call someone other than a Skype, et al, caller, no worries. Skype has a service called SkypeOut that allows you to purchase "credits" that permit you to call landlines and cell phones. Essentially, you are pre-purchasing calling time from Skype. Their site has complete details. www.skype.com
4) A PC to connect your player to. This is where the real "magic" comes in. The PC doesn't even have to be your own. If you are in an Internet Cafe and need to make a VoIP call, all you need to do is have a PC with a USB port that you can plug into.

Now, what you are going to do is connect your player to your PC and download a softphone client. However, instead of downloading it to your "C" drive, save it to your external, the player, drive. All installation should occur on the player. When the installtion setup begins, tell it to use drive "x"...X being whatever drive your player is designated as.

MPlat offers a small device that accomplishes all of the above. Literally, it is a small thumbdrive with a sound card, plus earphones. It looks for all the world like an inexpensive MP3 player.
From their website, they detail the install process

Quite honestly, it's that simple.