The iPhone hubpages app at this time can only browse forum activity through the feed.
You can change your feed settings so that you see recent activity in:
* posts you made
* topics that you posted on
* by users you are following
* forum of topics that you are following
To do this, go to:
and then click: "edit" after "FILTER BY TYPE"
In the next version of the application (coming out next month), you will be able to change these settings from the mobile app.