With temperatures rising to the 90s in Los Angeles, avoiding the heat wasn’t exactly an option while I was at a relative’s outdoor party in August. So I sat beneath a patio umbrella with a powerful fan nearby, figuring I was protected from the sun and heat. Half an hour later, I felt exhausted, dizzy, nauseous, and generally unwell, symptoms consistent with heat exhaustion.

Around the same time, I received a notification from an app used by the $249 ($149 at the time of publication) UV-tracking necklace I’d been wearing, called Gem, from a company called The90. It warned that my UV exposure had climbed considerably. It turns out UV radiatio …

Read the full story at The Verge.