bbPress.org

I migrated from phpbb to bbpress. phpbb had a watch topic mod which would send an email whenever a reply happens on a topic. I was just wondering if there is like a “Watch Topic” plugin. I know there is a summon user but this does not help me because I want to summon whole groups of people. I know bbpress is young, I was just wondering if anybody was working on something like this. My users dont use RSS unfortunately.