I have a private WordPress site with many of these things, including:

- A countdown to various events in the future (end of the quarter, next birthday, age 50, etc.) as a kind of "memento mori"

- Tracking money spent, food consumed, etc.

- A custom system that displays random items that I add to Anki every day. I explained this more in a comment from a few months ago: https://news.ycombinator.com/item?id=35211448

The data collection is pretty basic and just uses a form plugin to input and display data. I use other tools for to-dos, but I'm looking into a to-do plugin to replicate something similar.