Google announced browser-based Google Talk for the Apple iPhone and iPod Touch today. Although it‘s not in the form of an iPhone application, using the iPhone scripting libraries Google created a similiar environment on your iPhone than what you used to on your desktop. In your iPhone browser, just go to www.google.com/talk, sign in and start chatting. Typing on your iPhone screen is quite tedious hopefully the screen keyboard is better with the iPhone 3G.
Since this is a web app, Google Talk for the iPhone only works when it is the active window in Mobile Safari. Close the web broswer, or switch to a different window and you‘ll show up as unavailable in Google Talk.
With such a basic service why did it take Google Labs so long to release a iPhone enabled GTalk, perhaps they are saving the best for their own Android?