The BP Group Hierarchy Propagate plugin enables propagation of Activity Items up, down or up and down a hierarchy of BuddyPress Groups established by the BP Group Hierarchy plugin.
Note: this plugin has been developed and tested using BuddyPress 1.7+ and requires at least BP Group Hierarchy 1.4.2 if you want to switch the direction of propagation. The switch can be found on the BP Group Hierarchy settings page.
If you’re a developer, I’d welcome your contributions via the Github repo.