While many wearables are racing to add AI to everything, a company called The90 is focused on a single job of helping people keep track of their exposure to UVA and UVB rays throughout the day. The company has created a pendant-style necklace with a built-in UV sensor called The90 Gem. It works with a mobile app to track how much sun your skin is actually getting in real time.
Why UV tracking matters
The company says up to 90% of visible skin aging and premature skin damage is linked to cumulative, everyday UV exposure. UVA rays are associated with long-term skin aging and can pass through windows, while UVB rays are more closely connected to sunburn. That makes both types of exposure important, even when someone is not spending hours at the beach.
The90 Gem tracks live UVA and UVB data and feeds it into The90 app, where users can build a personal skin profile. The app takes into account skin type, sunscreen use, and sun-protective habits to offer more tailored guidance.
A necklace built for sun exposure, not notifications
The90 says the wearable can provide personalized UV thresholds, sunscreen reapplication reminders, and guidance on safer sunlight exposure windows based on real-time conditions. This helps users make more informed decisions about sunscreen timing and daily UV exposure.

The90 Gem is designed as modular smart jewelry, so it can be styled and worn like a regular pendant. The company claims up to seven days of battery life, a two-hour charging time, and splash resistance, though it advises users not to fully submerge the necklace.
The90 Gem is available now for $299, with an exclusive $199 early access offer, which can be available through their website. It comes in gold and silver colors.

