Medicare femSense Ovulation Tracker. The Medicare femSense Ovulation Tracker patch measures your body temperature 24/7 during your fertile window, the algorithm interprets the temperature measurements, and the app gives you daily updates on your fertility status.. The app tells you which days you are most likely to get pregnant and notifies you when ovulation has occurred.. The disposable temperature patch is worn under the arm for a period of up to 7 days when a woman is most fertile, during this time it continuously measures, records and analyses body temperature data. This data is then transferred from the patch to the phone when scanned using NFC (contactless).