Use this link –> http://hostedtalkgadget.google.com/a/COMPANY.COM/talkgadget/popout but replace [COMPANY.COM] with your domain for using Gtalk as gadget in your computer. If you want to access Google Talk on iPhone or any other mobile for Google Apps account, then follow these steps:

  1. Go to http://google.com/m/a/COMPANY.COM where COMPANY.COM is your domain
  2. Tap on more link
  3. Tap the Google Talk icon to chat with your Apps account. or go to this link on mobile phones –> https://hostedtalkgadget.google.com/a/COMPANY.COM/talkgadget/m That’s all folks. Just bookmark this link for using Gtalk over Google Apps account on the fly.
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