Daysy

Daysy is a biometric fertility awareness device designed for those who want to understand and work with their menstrual cycles without using hormones. It combines a precise basal body temperature sensor with a robust algorithm (the Fertility Tracker Method) trained on millions of cycles to determine each day whether you’re likely fertile, infertile, or in a learning phase.

Using Daysy is simple: each morning you measure your basal body temperature and log when your period starts. Daysy then lights up red when you are fertile (or possibly fertile) and green when you are not. If the device shows yellow, it’s still learning your cycle’s patterns.

Because it’s subscription‑free (the accompanying app is free) and built on decades of research, Daysy offers a more reliable, low‑maintenance way to monitor fertility, cycle health, and reproductive well‑being. It’s especially fitting for biohackers and longevity seekers who want more control over their physiology using non‑invasive, data‑driven tools.