Libjingle

Google releases Libjingle, the API for Google Talk Voice and P2P Interoperability, which will allow third party applications to interoperate with Google Talk’s peer-to-peer and voice calling capabilities. The package includes source code for Google’s implementation of Jingle and Jingle-Audio, two proposed extensions to the XMPP standard that are currently available in experimental draft form.
ZDNet’s IP Telephony blog has an interesting analysis of Jingle Audio, and Jingle Signalling in particular.

The fact that Google is seeking to integrate third-party, Jingle builds into Google Talk is a monumentally obvious indicator of how they hope to use third-party applications to bulk up their existing Google Talk and make it PSTN compatible.