Daysy is a one-button cycle tracker. Place under your tongue. Wait 60 seconds. See where you are in your cycle. No subscription, no hormones, no data shared with anyone, ever.
Your wearable tracks heart rate, sleep, and skin temperature at your wrist or finger. Those signals are real, but they aren't the signal your cycle runs on. Daysy reads basal body temperature orally with research-grade precision.
Basal body temperature rises by about 0.5°F right after ovulation. Detecting it reliably requires three things: the right place (under the tongue, not at the wrist), the right time (the moment you wake), and the right precision (±0.05°C).
Wrist and finger wearables don't measure under the tongue. They measure skin temperature, which drifts with the room, the blankets, and your activity. That's why the same Oura ring that gives you a great sleep score gives you a 4-day ovulation window. Daysy gives you the day.
Read the science behind the differenceSame Swiss sensor. Same 40 years of cycle science. Every one is a one-time purchase. None has a subscription.
App-connected. Cycle history, charts, and patterns at your fingertips.
Completely app-free. Everything happens on the device, nothing leaves it.
Pocket-sized and app-free. Fits in any bag, ready for travel.
Not sure which one fits your life?
Take the 2-minute fit checkDaysy customers come to us at very different moments in life. These are three.
"Ten years on the pill. The first three months off, I didn't know my own body anymore. Daysy gave me language for what was actually happening."
"Four months of trying, OPKs everywhere, charts I couldn't read. Bought Daysy and saw my first confident window in cycle two. Pregnant by cycle five."
"Second baby, 4am wakeups, no routine. Every cycle app was useless to me. Daysy quietly figured out my new pattern in two cycles."
Valley Electronics was founded in Zollikon, Switzerland, by Dr. Hubertus Rechberg, a physicist who wanted to help his wife understand her cycle. Forty years later, we're still in Zollikon, still family-run, and still building one kind of device.
We've never taken venture capital. Never been acquired. Never added a subscription tier. We ship from a small warehouse in Centreville, Maryland, and answer the phone when you call.
Read the full storyOne-time purchase. No subscription. Free US shipping. 30-day money-back guarantee. Spring Sale prices through May 31.
Ancient knowledge married with modern technology.