Today gmail has announced and rolled out this feature yes there were many alternatives like Pidgin, Empathy with this feature long back, but it's still nice to see this in the browser, enable this feature from here

Hope to see Gtalk for GNU/Linux users one fine day like today!

The Controls looks so.

Me trying the plugin for FF [ browser restart required ]:

Updates :
@gmail Thanks for the V&V plugin, if two friends F1 and F2 are both invisible, how do they make VC? BTW is there a V&V test bot ? #gmail