Leaf Nature Activity & Health Tracker Tan/Silver. Leaf Nature is a health tracker designed as jewelry. It places a focus on mind-body balance as the key to your well-being. Leaf helps you understand whatâ??s going on with your body and helps you take control of your health, forming positive habits that will last a lifetime. The Leaf is a sleep, activity and reproductive health monitor that helps you cope with stress through built-in breathing exercises. This smart piece of jewelry works as a tracking system for your health and provides insights and helpful reminders to keep you on track. Monthly cycles (fertile days, ovulation, period, and contraception intake) are tracked through the app so that you can have greater awareness of your reproductive health. It can be worn as a necklace, a bracelet, or a clip.