On the CUNY Academic Commons we have a MediaWiki installation running parallel to our WordPress/BuddyPress installation. In the past I had hacked together an inelegant and constantly breaking solution for importing wiki edit notifications into the BP activity stream. I’ve just written a small plugin called BP External Activity which solves the problem by using the BP activity API and RSS.
The plugin can be used to pull items from any RSS feed and add them to your BP activity stream, with customizable text. It’s feature-light right now (and requires some hand-coding to work) but it’s still pretty much the coolest thing ever. I will update it to be better when I get around to it.