Google launched the gtalk iphone application on July 09 which lets you talk to your friends on gtalk from your iphone.You can sign into gtalk right from your safari browser and will automatically be signed out if you leave the window or browse to some other google application.

“Because this version of Talk is designed to run in your browser, you’ll be automatically signed out of Talk when you navigate to a different browser window or iPhone app. So while it’s not a traditional “always-on” instant message client, it’s useful for changing your status message on the go or checking in to see if someone’s online and sending them a quick chat. It’s equally nice for killing time at the airport.”’

Google Apps users: visit http://talkgadget.google.com/a/your-domain.com/talkgadget/m from your iPhone’s browser, but be sure to replace ‘your-domain.com’ with your actual domain name.