Cortisol+ - The cortisol tracker your Apple Watch was missing

Hey Product Hunt 👋 I built Cortisol+ because I was burning out and my Apple Watch wasn't telling me. It tracked my heart rate, my sleep, my workouts — but the signal I actually wanted to understand was cortisol. And no consumer wearable measures cortisol directly. It's a hormone, not an electrical signal. Here's the thing though: Apple Watch already collects every biometric that's correlated with cortisol. HRV. Sleep stages. Resting heart rate. Wrist temperature. Recovery balance. The data is sitting there. Cortisol+ combines those signals into a continuous cortisol-pattern estimate, calibrated to your personal baseline. You get a 0–100 cortisol score, updated in real time, mapped to four levels (Low, Normal, Elevated, High) — visible on iPhone and on the Watch face itself. A few things I'm proud of: → It's honest about what it is. We don't measure cortisol — we estimate the pattern. Every page on cortisolplus.com says so. No "AI-powered" smoke. → Sleep × cortisol analysis. Most stress apps treat sleep as a separate metric. We treat it as the biggest driver. You see exactly which nights spike your next-day cortisol. → Zen mode with measurement. Guided breathwork that shows you the HRV recovery curve after each session. You see the cortisol drop, not just hope for it. → On-device privacy. Biometric data stays on your iPhone. We don't sell it. No Meta pixel, no Google Analytics in the app. → Free to download. Premium subscription for advanced features, but the core cortisol score is free. Where we are: 5,000+ users, 4.9 stars across 16 ratings, available in 171 countries. A few things I'd love feedback on from this community: 1. If you have an Apple Watch and try the app, does the cortisol score actually match how you feel that day? 2. What's the one cortisol-related question you've always wanted answered but no tool has helped with? 3. For the iOS devs here — anything you'd build differently with the HealthKit data we're using? Genuinely excited to be in front of this community. Will be in the comments all day to answer anything. Thanks for taking a look 🙏 — Mikah Founder, Cortisol+ (Elevated Systems LLC) cortisolplus.com