“Plastic ring” and “vaginal temperature sensor” might not be the sexiest words, but the Ovularing, a medical cycle tracker, is all about your sex life. Because whether you’re trying to get pregnant or trying to make sure you don’t, you are part of the target group for this device. The Ovularing enables you to work out exactly when you’re ovulating, to better understand your cycle and support natural contraception. This is just one of a slew of products that help you track your fertility without using a regular thermometer (the traditional tool used by women for decades to figure out their cycl…