If iOS Reminder is completed, add an entry to Day One Journal by a combination of Hazel and Gadgetcoma's IFTTT Day One (giftttdy) logger. See HIS blog http://gadgetcoma.com for details. This is great stuff! Thank you gadgetcoma!

This Trigger fires every time any reminder is completed.

This Action will create a new text file at the path you specify.

If iOS Reminder is completed, add an entry to Day One Journal, via giftttdy and Dropbox