When you try to use Google Talk on your iphone with a Google App hosted domain, it insists that you use an @gmail.com account.
The [not publicized] URL to get past this is
http://hostedtalkgadget.google.com/a/DOMAIN/talkgadget/m
Just replace DOMAIN with your domain. And you can get on Google talk on your iPhone or iPod touch on your Google App hosted domain.
