Hey Product Hunt, I build medical AI for a living, which means I spend a lot of time thinking about health data, who collects it, who owns it, and who almost never sees it: the person it's actually about. A few weekends ago, I went down a rabbit hole on my own phone. I wanted to know exactly how much data it was collecting about me every day. It's a lot. Steps. Location. App usage. Screen time. Sleep patterns inferred from when I plug in my phone at night. Activity recognition. Health Connect records syncing in the background from apps I'd forgotten I installed. Most of it flows into systems built by big companies that use it to optimize their products. You can't really turn it off. It's how modern phones are built. But here's the thing that struck me: that data is genuinely valuable. Not to advertisers. To the person it belongs to. The patterns in how you move, sleep, and use your phone tell a real story about your health, your routines, and your life. If you could see that story clearly, you could actually use it, to notice when you're drifting, to understand what good weeks look like, to become a slightly better version of yourself. The problem isn't that the data exists. The problem is that you don't own it, can't see it, and can't use it. So I built Zentra. Three rules, non-negotiable: 🔒 Everything stays on your device. No cloud. No accounts. No telemetry. The app doesn't even have permission to access the internet — the Android manifest literally doesn't declare it. 📦 You own your data. Export it any time, in clean CSV or JSON, over any date range. 🕯️ No nagging. No streaks, no notifications, no gamification. Zentra is a vault, not a feed. And because "trust me" isn't good enough for health data, the whole project is open source. You can read every line of code, verify the privacy claims yourself, and build it from source if you want. Currently available as an APK on GitHub Releases, with F-Droid and Play Store distribution coming soon. iOS is on the roadmap. I'd love to hear what you think, especially: → What data sources do you wish Zentra captured that it doesn't yet? → Have you tried other privacy-first health tools? What worked and what didn't? → If you're on iOS and sad you can't use this yet: 👋 I see you. Soon. And if you try it and find bugs, please open an issue on GitHub. Every bug report from day one helps shape the project. Thanks for checking it out. 🙏 — Joshua

Zentra

The health dashboard your phone was supposed to have.

The health dashboard your phone was supposed to have.