It would be very useful to be able to tie conditions in the Attendance module to the Moodle messaging system, to automate notices to students based on attendance data. For example, to send a pre-defined message to a student if she/he has two absences recorded for the course.
From a user interface perspective, I would see a Notifications tab added after the Reports tab in the instructor view of the module. The Notifications tab would allow an instructor to define notifications for the specific course -> what are the criteria (e.g. number of absences) and what is the message text to be sent out as a notification when a student hits that criterion. The Notifications tab would allow multiple notifications to be set up for a course, for example, a warning message when a student accumulates 2 absences and a notice of failing the course when 5 absences have accumulated.
I initially thought this might have to be a Cron job, but it probably makes more sense to just have it triggered when an instructor submits a session's attendance data. Submitting attendance data for a class session could cause the module to check to see if any students have hit the criterion for a notification, and send the defined message for that notification out to the student. The data tables for the module would have to keep track of which students have received which nofications, so that a student with eg, 2 absences only gets the warning notification once, and not every time thereafter that the instructor submits attendance data for later class sessions.