Back in the beginning of the summer Alain Knaebel and Matthieu
Helleringer worked on support for GMail notifications.
I have spent some time on integrating and extending their code during
the last week and I've just committed (r5937) it. You need to enable it
from the XMPP account wizard but once you do it is supposed to work for
both GMail and Google Apps.
There seems to be some kind of a problem though because I only get mail
reports when I explicitly ask for them. In other words I am only seeing
the <mailbox> IQ from  and never come across the <new-mail> one.
I suspect this has something to do with my smack IQ provider and/or my
packet listener because back in spring Alain and Matthieu told me it
worked for them. I won't be able to look at this in the following days
or weeks though so if anyone else would like to give it a try then