Here at Istos we would love to see a set of Drupal 7 modules that provide support for the complete OStatus stack and see where FOAF ssl could fit into that. The first step we are working towards at is to provide support for Activity Streams for the Drupal 7 port of the Activity module (thanks Scott!). Then we would like to combine these with the PubSubHubbub work to have a working example of Drupal users across Drupal sites subscribing to each other's activity streams.