We actually built a plugin for that function, wich was based on eventpress from kunal! It worked for a while, but we are rebuilding it using custom post! We believe on that, and the powerful from having your own custom post to update with wordpress and no depending of others plugin that can be updated or NOT.
I suggest to programmers to try one thing, on buddypress links when you introduce a link adress, the plugins detect rich media and fetch the address could be that de eureka of the matter if we could say to activity stream that each link get the same fetch and publish. Its not easy i guess, because im not really into programming, but I feel its the correct answer.