Gem Necklace Tracks UV Exposure, Catches Heat Exhaustion Clue

A $249 UV-tracking necklace called Gem flagged a spike in sun exposure just as its wearer began showing signs of heat exhaustion at an outdoor party in Los Angeles this past August, according to a hands-on account by Sheena Vasani, a commerce writer at The Verge.

Vasani had strapped on the device, made by a company called The90, expecting to learn something about how sunlight was aging her skin. Instead, the pendant turned into an early-warning system for a medical episode she had not anticipated.

What Is the Gem Necklace and How Does It Work?

Gem is a wearable sensor paired with a smartphone app that monitors ultraviolet exposure in real time and sends alerts when levels climb. The90 lists the necklace at $249, though Vasani noted it was selling for $149 at the time her piece published, per The Verge.

How Did a UV Tracker Catch a Heat Exhaustion Episode?

Vasani sat under a patio umbrella with a fan running nearby, assuming she was shielded from both heat and sun. Roughly 30 minutes later, she felt "exhausted, dizzy, nauseous, and generally unwell, symptoms consistent with heat exhaustion," she wrote. Around the same time, the Gem app sent a notification that her UV exposure had climbed considerably — even though she was sitting in shade.

"What started as a test to understand how sun exposure was aging my skin took a turn that I wasn't expecting."

Can Shade and a Fan Actually Block UV Radiation?

Not reliably, Vasani learned. UV radiation can be reflected or scattered by surfaces in the environment, meaning a patio umbrella does not guarantee protection the way it might seem to. She had assumed shade plus airflow would cover both sun and heat exposure; the umbrella addressed neither as fully as expected.

What Did a Medication Have to Do With It?

The episode led Vasani to a separate discovery: one of her medications increases sensitivity to heat, a factor she had not previously connected to her outdoor comfort. UV exposure and overheating are distinct physiological processes, she wrote, but her experience showed how easily the two can be conflated when neither is being measured directly.

Gem Necklace at a Glance

• List price: $249
• Price at time of testing: $149
• Time before symptoms appeared: about 30 minutes under shade with a fan running

Is the Gem Worth It for Sun Safety?

The Verge's account frames Gem less as a vanity skin-aging gadget and more as a early-warning tool for conditions people assume are under control. For anyone on medication that affects heat tolerance, or anyone who equates shade with full protection, a continuous reading — rather than a guess — appears to be the device's real value, based on Vasani's experience.

The full hands-on account, including additional impressions of the Gem app and design, is available at The Verge.

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