Any ideas on how to distribute course completion certificates?

I would like students to receive a certificate of completion when they submit the last assignment of my iTunes U course. There is no way to fail the course. This course if for completion only. I will never see the majority of the students, all of whom will be progressing through the course at radically different times. I do not have the capacity to constantly monitor for the course being completed by individuals nor generate certificates by hand.

Any ideas on how to automate distribution of a certificate of completion?