Here is a smart wearable device for fertility tracking. The YONO happens to be a wearable basal thermometer that sits in your ear, creating an enclosed area in your ear canal to prevent external factors to affect its measurements. It measures your core body temperature instead of skin temperature for more accuracy.
YONO does not feature Bluetooth but has a smart Base Station that lets you sync your data easily. The companion app provides you with useful data and charts on your iOS or Android device. More information is available on Kickstarter.