Wearable devices are moving beyond steps, sleep, and heart rate. The90’s Gem takes that shift in a more specific direction, tracking real-time sun exposure so users know when to reapply sunscreen, seek shade, or limit UV exposure.
The device is designed as a circular sensor set inside a titanium case and worn as a pendant. It comes in silver or gold and is built to look more like an accessory than a medical gadget.
Why Gem stands out
Gem focuses on a problem that many people still manage by guesswork: how much ultraviolet light actually reaches the skin during daily activities. Instead of relying only on a general UV Index, the pendant measures the exposure a user receives in real-world settings.
The system tracks both UVA and UVB, the two main forms of ultraviolet radiation. UVA is associated with long-term skin aging, while UVB is linked to sunburn and immediate damage.
The90 says the sensor continues working in places where sun protection is often assumed, including inside a car, near a window, in shade, or at the beach. That makes the reading more personal than a local weather-based UV estimate.
How the companion app works
Gem connects to an Android and iOS app that begins with a questionnaire about skin type and sunscreen use. From there, the app gives real-time exposure data and flags when sunscreen should be reapplied or when it is time to cover up.
The software also helps users judge whether shade is truly reducing exposure. It includes a vitamin D target, clothing guidance for current UV conditions, and suggestions for what to do after time in the sun.
That approach turns sunscreen from a once-a-day routine into a more responsive system. The goal is to help users react to the UV load they are actually receiving, not just the forecast.
Designed for everyday wear
The90 was founded by Stacy Salvi, a Fitbit veteran who also worked at health technology company Movano. She previously took part in the development of the Evie smart ring, another wearable created with women in mind.
The company says its first focus is women, but it plans to introduce versions for men and children, along with additional wearing formats beyond the pendant design. Salvi has said the product should pair premium aesthetics with modular design so it is something women actually want to wear.
Gem also includes practical hardware details. The battery is claimed to last about one week on a single charge, and the sensor and casing are splash proof.
Price and availability
Gem is already available for preorder at $299. Early buyers can get it for $199, and The90 says there is no mandatory subscription fee for current features.
The company has left open the possibility of paid add-ons in the future, but only for users who want access to new features. For now, the existing functions remain free.
By targeting UV exposure instead of broader fitness metrics, Gem shows how wearable technology is becoming more specialized and personal. It is aimed at a daily health concern that many people still estimate by instinct, even though the skin often absorbs more sun than expected.