The90 drops Gem, a smart pendant to track your UV exposure

Health tech startup The90 is zeroing in on an overlooked category in the massive health tracker market: skin health. Its new product, The90 Gem, is designed to measure UVA and UVB exposure, giving users a more direct way to understand how sunlight affects their skin over time.

While sun exposure is often reduced to the UV index in a weather app, the brand argues that approach misses a lot, especially when it comes to actual exposure, skin type, and the role UVA plays in skin aging.

How it works

On the outside, Gem just looks like a standard pendant necklace and measures about the size of a US nickel, in either gold or silver finish. The black center is what houses the continuous UV sensor. Rather than tracking fitness metrics, the device captures the exact amount of UVA and UVB rays hitting your skin in real time.

That data then syncs via Bluetooth to a companion app that organizes your data into a few core functions:

• Exposure tracking: The dashboard breaks your daily sun exposure down into protected and unprotected minutes.
• SPF integration: You can log your specific sunscreen SPF in the app, which then calculates a precise safe-sun window.
• Real-time alerts: The system monitors immediate burn risk and long-term aging impact, sending a notification when it is time to reapply or seek shade.

For daily wear, the splash-proof pendant runs for a full week on a two-hour charge.

The wearable market is completely saturated with fitness trackers, but The90 makes the case that skin health deserves its own device. Still, by disguising the UV sensor as a classic gold or silver pendant, it rides the same lifestyle-jewelry wave we’ve seen from Oura and Whoop’s recent designer collabs.

Where to get it

The90 Gem is available through the90.com.