Need to customize activites module to generate a certain activites feeds

We have implemented the flag module as a way for users to add each other as their friend (by flagging their bio module). We are looking for a way to create an activities feed that filters activities of the users friends. We think that this would be a very valuable and compelling feature and would love to help contribute it back to the community. If you happen to know the ins and outs of the activities modules and flag module, we would love to have your help on this. Looking forward to hearing back soon!