There is a new feature (currently only for Activities) that allows you to send the group leader a letter upon completion of an activity.
In the activity set up you need to select the letter from /letters/co to send, optional header and footer files, and the subject.
Once per hour the system scans for any Activities that have completed, Start time + Duration (hours), and any letters are sent. As well, a summary of letters sent is emailed to your admin email account.