I’ve been using org-mode capture templates for years and I’ve always wished I had something like that for the whole system. I took advantage of the holiday break to build Remember, a little reminders application with Spotlight-like UX. It’s available on Gumroad and you can pay what you want for it (inlcuding $0!) at the moment so I hope you’ll give it a go!
Although the app isn’t Open Source, it source code is available on GitHub. Feel free to build, modify and run it yourself, but please don’t redistribute it.
P.S. the app is currently on Product Hunt so if you have an account there, feel free to leave a comment!