Most men check their testosterone once a year — at best. But T levels fluctuate 30–50% throughout the day and are one of the earliest signals of energy, mood, and metabolic health. MOJO KING estimates your testosterone daily using your Apple Watch's PPG sensor and HRV patterns. No blood draw. No clinic visit. 15 seconds on your wrist.

Wispr Flow: Dictation That Works Everywhere — Stop typing. Start speaking. 4x faster.

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Hey Product Hunt! 👋 Sungjin here, founder of MOJO KING and 6Letters. I spent 15 years running clinical trials across pharma — biourology, endocrinology, cardiovascular, CNS — before building this. The question that kept bothering me: why can we track sleep, heart rate, and glucose in real time, but testosterone — which drives energy, mood, libido, and metabolism — still requires a clinic visit once a year? That gap is what MOJO KING is built to close. A few things I'd love honest feedback on from this community: Does daily T trend data change how you'd manage your health? What would make you trust (or not trust) a wearable hormone estimate? What features would make you actually pay for this? The app is free to try — no blood draw, no clinic, just your Apple Watch. Ask me anything about the science, the model, or why we built this. I'll be here all day on launch day to respond to every comment. — Sungjin, CEO of 6Letters

Wispr Flow: Dictation That Works Everywhere — Stop typing. Start speaking. 4x faster.

Stop typing. Start speaking. 4x faster.

MOJO KING

Your Apple Watch can now estimate your testosterone. Daily.

Your Apple Watch can now estimate your testosterone. Daily.