UV Tracker: A Necklace Measures Skin Aging

The90 has launched a wearable device designed to quantify personal exposure to ultraviolet radiation. The product, called the Gem, is a necklace that costs $249. It measures two specific types of UV light, UVA and UVB, and sends that data to a smartphone application.

The company argues that most consumers track only visible sunburns or cosmetic aging. The Gem attempts to provide a more granular view of how sunlight affects the body. It separates the radiation that causes sunburn from the radiation that contributes to premature skin aging. UVB is linked to vitamin D production and burns, while UVA drives aging effects even without a visible redness.

During a review period in August, a tester in Los Angeles used the device to challenge common assumptions about outdoor safety. The tester sat under a patio umbrella during a hot afternoon. They believed the structure and a nearby fan would block the intense solar radiation. After thirty minutes, the tester experienced dizziness and nausea. A notification from the device indicated that UV radiation had penetrated the shade. The umbrella did not block all light because surrounding objects reflected and scattered the rays.

The hardware is a circular pendant on a titanium chain. Users can choose between gold or silver tones. The company designed the item to look like a standard fashion accessory rather than a technical gadget. The battery lasts approximately one week and recharges on a provided dock. The sensor does not store data internally. The mobile application must run in the background on an iPhone to record readings. If the app is closed, the device may fail to log time spent outside.

The application translates raw sensor data into graphs and plain language. It calculates a daily Sun Score that balances the benefits of sunlight against the risks of overexposure. The company recommends aiming for a score of 90. The app also provides a personalized sunburn countdown and a Skin Aging Zone. This zone assesses the risk of aging and offers specific skincare advice. Users can input details about their skin type and clothing to refine the estimates. These metrics are predictions rather than direct biological measurements.

The tester found that the individual data points were more useful than the overall score. The estimated measurements for vitamin D production and circadian light benefits offered specific insights. The vitamin D countdown proved difficult to use because the numbers fluctuated rapidly with changing UVB intensity. The tester focused instead on the cumulative exposure patterns. The data showed that UVB accumulation over a typical week was lower than expected, even for someone living in a sunny coastal city.

This finding prompted the tester to investigate how melanin affects vitamin D production. The user previously focused on avoiding sun exposure to prevent aging. The device data shifted their perspective toward the health benefits of moderate sunlight. The tester began to consider how hydration and timing of outdoor activities impact comfort and safety. The realization that a specific medication increased their heat sensitivity also explained previous episodes of discomfort.

The Gem does not require a monthly subscription fee. The one-time cost of $249 is a premium price point for a wearable. The company acknowledges that the device is best suited for individuals who are active outdoors. It may be a difficult purchase for people who spend most of their time indoors. The price was temporarily reduced to $149 during the initial review period.

The90 plans to release alternative form factors in early 2027. The company intends to sell a hat clip and a bag tag version of the sensor. These accessories will allow users to track exposure without wearing a necklace. The Gem remains available now as a tool for tracking the complex relationship between UV radiation and personal health.