Tuesday afternoon at three o’clock, the sun is just right. You’ve just finished a lap in the park with your child, and you glance down at your smartwatch: heart rate, steps, sleep score are all clear. But how much UV have you been exposed to today? The watch tells you: I don’t know.

That’s the problem. Weather apps give the average UV index for the entire area, not the actual exposure where you’re standing on the sidelines of the soccer field; you’ve had the sunscreen for half a year, but whether you’ve applied enough or need to reapply is all based on feeling. UV, this “invisible opponent,” finally has a way to be tracked.

Separate UVA and UVB to Truly Understand Sunscreen

The90 Gem is a wearable UV sensor shaped like jewelry that can be clipped into a gold or silver necklace pendant. Its most special feature is that it detects UVA and UVB separately, rather than mixing them into one vague number.

Why is this important?

• UVA is mainly related to skin aging; it can penetrate glass and clouds, the “invisible aging driver”
• UVB is the main cause of sunburn and also key for the body to synthesize vitamin D

The traditional UV Index leans toward sunburn assessment and often underestimates the long-term cumulative damage from UVA. The90 Gem directly tracks these two types of UV separately, letting you see the real risks to guard against.

Your Daily Sunscreen Finally Has Real-Time Data Support

Paired with the free app, Gem converts the sensed data into:

• Daily cumulative UVA and UVB exposure
• Countdown to estimated time until sunburn
• Personalized sunscreen reapplication reminders (not an alarm, but triggered based on your actual exposure)
• Daily “Sun Score” sunlight score (0-100 points)

Imagine this scenario: On Saturday afternoon, you’re chatting with friends at an outdoor seat at a cafe, and your phone pops up a notification: “Based on your current exposure, we recommend reapplying sunscreen in 15 minutes.” Not based on feeling, not on the weather forecast, but truly based on real-time data of your location and duration.

Not Just a Necklace, But Your Skin Health Assistant

There are UV sensors on the market, but most have been discontinued (like La Roche-Posay’s My Skin Track UV), or require extra attachment to an Apple Watch band. The90 Gem achieves all-day wear, real-time monitoring, independent operation, while retaining the aesthetic of jewelry accessories.

What can it do?

• Track daily actual UV exposure, no longer relying on rough weather forecast numbers
• Estimate vitamin D production based on skin tone and exposure time
• Sunscreen reapplication reminders to avoid overexposure or insufficient protection
• Long-term data accumulation to help you build smarter sunscreen habits

Of course, Gem is not magic. The official statement clearly says it “cannot replace sunscreen, coverings, or basic common sense,” and vitamin D data is also calculated based on your skin type and exposure conditions. But the point is not to replace, but to stop you from being blind.

Who Should Wear UV on Their Body?

The90 Gem is priced at $249, which is not cheap for a single-function accessory. But if you belong to the following groups, it might become the next piece of your daily health tracking puzzle:

• Parents who work, exercise, or accompany children outdoors for long periods
• Those undergoing anti-aging care who want to precisely control UVA accumulation
• Skincare enthusiasts concerned about vitamin D intake who want to balance sun exposure and sunscreen
• Tech enthusiasts who already wear smartwatches but want to supplement with “environmental health data”

Invisible UV Rays Deserve to Be Seen

Our smartwatches can tell us how well we sleep or how stressed we are, but know nothing about the UV rays shining on us every day. The90 Gem fills in this missing piece. It’s not about making you hide from the sun all day, but letting you enjoy the sunlight while clearly knowing where the boundaries are.

When sunscreen goes from “guessing” to “data,” your skin will thank you for every decision you make.