Declining to announce any plans for a native chat client at this point, Google has announced a Web-based, iPhone-optimized version of Google Talk. A company blog posting reads:
"Our new version of Google Talk is designed specifically for the iPhone and runs in the iPhone's browser, so you don't need to download or install anything. Just visit www.google.com/talk on your iPhone, sign in, and start chatting. And because it is built for the browser, it will work on today's iPhones as well as on tomorrow's 3G iPhones."