If you use skype for chat purposes, there are adapters you can buy that allow you to connect any ordinary telephone to your computer and use it for audio and dialing purposes:
http://www.voipsupply.com/prod...o.php?products_id=1607 is an example of the type.
If you use SIP based VOIP, you can get networked telephone adapters for surprisingly little:
http://www.voipsupply.com/prod...nfo.php?products_id=35 is more or less representative.
In either of those cases, you would just use any ordinary cordless phone. For some reason, cordless voice transmission seems to get less expensive in full phone form than in limited headset form, no idea why. However, none of these would appear as an ordinary mic in/audio out sound device from the OS' perspective, so don't be led astray if that is what you need.