I take it you mean google's tasks, but to my knowledge there is no way of syncing that straight from OF/iPhone since Google tasks can't read from an Omnifocus sync file if you were to use a WebDAV server (or Mobile Me). You could always check out Google's forums, but I really doubt that it is possible. To see what's possible in Omnifocus for iPhone "as is" check the
manual from Omni's web page