Dutch start-up e-Senses, in collaboration with Holst Centre, has developed the world’s first personal sunlight, daylight and vitamin D coach. The Helios smart ring gives wearers feedback on the amount of sunlight they receive and how much vitamin D they create, personalized to their skin type and behavior. It lets people find the perfect balance between sun safety and getting enough vitamin D.   Vitamin D is essential for strong teeth, muscles and bones, and has been shown to help prevent canc...