Sony has added Skype to the PSP. The Sony CES website says:
Call friends, talk trash to fellow gamers or catch up with acquaintances via Skype for PSP system.
PC Magazine says that the PSP supports both SkypeIn and SkypeOut, so the PSP can substitute for a phone when you are at home or somewhere else where you have Wi-Fi access.
This isn’t a breakthrough, just another feather in the scale, tipping us towards a world where just about any connected device can make an internet phone call. The speed of this evolution is governed by the enormous legacy public telephone network; because of Metcalfe’s law anything that aspires to be a useful substitute for the phone system must first interoperate with it.