The Correlate feature is what made it click for me. I found that my chemo side-effects peaked at an 8-day lag — not when the doctors said they would. I showed the chart to my oncologist and it changed the conversation from "I think the side-effects come later than you warned" to "here's the data."

Recently my CT scan showed all tumors shrinking for the first time. Digging into the data, the clearest signal is a sharp increase in daily steps over the past month — partly better weather, partly a new puppy who needed walking. Steps are a known predictor of cancer survival, and the correlation-with-lag tool made it easy to see the timing line up with my scan window.

There's also a premium AI Analyst tab (powered by Claude) that answers natural-language questions about your data and generates daily insight cards. It's how I pay the bills while I'm not working and fighting cancer — the core tracking and analytics are free.

The app is general-purpose. I use it for cancer, but it works for anything — habits, grades, mood, workouts, macro data. I wrote a separate post using it to find the 12-18 month lag between Fed rate changes and unemployment.

Free on iOS: https://apps.apple.com/us/app/meetrics/id6760925743 Full write-up with screenshots: https://github.com/sergeybok/meetrics-support/blob/main/BLOG... Would love feedback from the QS/data crowd here.