Ask HN: Most interesting tech you built for yourself?

I built a mental health tracker and a physical health tracker, that sit in my living room and use LEDs to display a prediction of how good my health is.

The mental health tracker keeps track of my sleep, and how long it takes me to do various things in the morning. The physical tracker keeps track of how much walking I'm doing and how often I'm doing certain exercises.

They have slightly different uses; with mental health I only really notice whether I'm feeling 'okay' or 'extremely bad', so seeing a far more granular estimate is useful. The physical health is more a reminder that it's time to do certain exercises to keep the back pain at bay for a bit longer.