Basal Body Temperature (BBT) is the lowest body temperature during sleep. Since 1930s, BBT has been used for fertility awareness. BBT is generally measured immediately after awakening and before any physical activity; the temperature measured at that time is usually higher than the true basal body temperature. The current accuracy of using BBT to estimate ovulation day is very low, because the data captured by conventional method is very hard to interpret. iFertracker – Smart Fertility Tracker is a wearable sensor that continuously captures the body temperature data every 4 seconds over night, and synchronizes the data automatically to the mobile app to record the basal body temperature. The mobile app provides ovulation charting, pregnancy possibility estimation, and sleep quality analysis. In addition, the cloud service will provide partner sharing, data access at anytime etc. One package contains: 1 device, 30 patches, 1 CR2025 battery, 1 battery tool, 1 user manual