People just don’t get as much sunshine as we used to. We work in offices or go to schools, rather than toiling in the fields. And when we do go outside, a healthy concern about skin cancer causes many of us to cover up or lather ourselves with sunscreen. The problem is that our bodies need some of the ultraviolet (UV) light in sunshine to make Vitamin D, a nutrient required for strong bones. It’s also available naturally in a limited number of foods, such as some fish and egg yolks. Health officials decided long ago to fortify some foods — such as milk — to help ward off Vitamin D deficiency, but changing diets mean that many people may not be getting enough of this essential vitamin.

SunFriend is a wearable Health Tech device that monitors how much exposure you’ve had to sunlight, and alerts you when it’s time to cover up, apply sunscreen, or simply go indoors. You adjust the wrist-worn device for your skin type, and then calibrate it by aiming it at the sun for 10 seconds. You can then go about your normal activities, making sure that the SunFriend is not covered up by your clothing. According to the company, the device tracks your exposure to direct and indirect UV. (As a sailor, this is an attractive feature since light reflected off the water contributes significantly to UV exposure.) You can check your accumulated exposure at any time by pressing a button and seeing how many of the 11 LEDs light up. When you have reached your limit for the day, all 11 LEDs will start flashing. When you turn off the device, it resets and is ready for the next day.

The SunFriend costs $50 and is available through Amazon.