Google hasn't released official Google Talk app for iPhone, iPod Touch and iPad yet. While Google Talk app for iDevices is still under development, Google has released the web-based mobile version of Google Talk optimized for Safari browser to use GT on iDevices.
All you need to do is to open Safari browser on your iPhone, iPod Touch or iPad and type www.google.com/talk in the address bar. You'll be prompted to sign in with your Google account.
Enter your Google account login and password. It will take a while to load your Google Talk contacts.
Once your contacts are visible on the screen, you can chat with them.
This Ajax version of Google Talk doesn't offer all chat features which are available in Google Talk desktop version like tabs, group chat, options to add contacts and send email etc. Moreover, if you close the Safari window, your status will be changed to unavailable.Contact Us for News Tips, Corrections and Feedback