Re: bbpress standalone in activity stream
The backpat plugin is only going to support the 1.1 branch of code, and not the dual theme massive integration headache that came before it.
To have the activity stream update when you post a topic or post a reply, bbPress would need a special plugin to be made, and/or bbPress would need to be “deeply” integrated with WordPress/BuddyPress to have those functions natively available.
The other thing you could do is look into previous versions of BuddyPress that included that kind of support. In BP 1.0 it was assumed that if you wanted forums, that you were using the voo-doo magic method of integrating things.