Care to share a screenshot and the 'killer feature' of any of your personal, self-built productivity tools? eg. I made my own calendar and money-tracker last year - there are no other users, it makes no money, I have no plans to make it public, but it holds my life together :)
http://i.imgur.com/h2keJDg.png
GREAT BECAUSE... it tells me how much I'm going to get paid this month.
Absolutely no ulterior motive here (ie. I'm not canvassing opinions for a productivity app startup or anything), just interested.