I built it to get email reminders about things that expire, such as passports, free trial cancellation dates, Covid antigen tests, travel reward and free night expiration dates, etc.

My real sob story is that my passport unknowingly expired and I didn't notice until I was checking in to an international flight. I really don't want that to happen again, especially now that I have more passports to keep track of in the family.

It's built with blitz.js, Go, Postgres, and runs on a tiny VPS. I use it for myself and haven't marketed it much.