I just about qualify! My first side project that actually delivered anything: Reminder Sync for Obsidian! https://turquoisehexagon.co.uk/remindersync/

I built it for myself after I began using Obsidian for day to day note making. A simple idea: get reminders for tasks you create in Obsidian. People seem to like it.

previous discussion: https://news.ycombinator.com/item?id=39764919