Wippien is Instant Messenger with VPN support, that combines different protocols - ICQ, MSN, AIM, Yahoo, Google Talk. It gives you ability to have several computers arround the world connected to isolated local LAN without any special setup. NAT traversal techniques are used to penetrate NAT devices and make direct connections between peers, and allows you to access your friend's resources (such as sytem shares, printers..). It uses XMPP/Jabber protocol to locate your friends and see their presence status, and after that it initiates direct peer-to-peer secured connections with them. None of peers need to know real IP address of other peer - Wippien assigns temporary one for the session lifetime. If if your friends don't use Wippien, you can still use Wippien as ordinary instant messenger - really good one!
Software that can be used as an alternative to Wippien: