My smartwatch knows how poorly I slept and how elevated my heart rate got during a stressful afternoon. But it can’t tell me how much UV exposure I accumulated on my walk to park. That’s the gap UV tracking wearables like The90 Gem aim to close. We’re exposed to UV light every day—shouldn’t we track it?
I live in a city that gets over 300 days of sunshine per year. That’s a lot of sun. Yet people here still treat sunscreen like a beach accessory. You buy it in June, forget it by October. But UV exposure doesn’t follow the tourist season.
What would a different approach look like?
The90 Gem is a wearable UV sensor that clicks into a gold or silver pendant and reads UVA and UVB separately, in real time. The free app turns that into daily UVA and UVB totals, an estimate of how long until you burn, and sunscreen reapplication reminders, plus a daily Sun Score from 0 to 100.
No, your weather app may not be enough. A local UV forecast describes what reaches city, not your exposure while watching your kids’ soccer practice.
The90 also notes that the standard UV Index is weighted toward sunburn, so it underreads the UVA—the light that ages skin.
Most wearables look inward: heart rate, sleep, blood oxygen. But our surroundings affect our health too, and UV’s two types do different things. UVA is mainly associated with skin aging, while UVB is mainly associated with sunburn. UVB is also what triggers vitamin D production in the skin. That’s why UVA and UVB monitoring beats one blended number.
We shouldn’t have to wait for a sunburn to think about how much sun we’ve had. Smartwatches aren’t completely blind here. The Microsoft Band had a UV sensor a decade ago, and accessories like this UV-sensing Apple Watch band add one today. But direct, all-day sun exposure monitoring still isn’t a mainstream feature on the health-tracking smartwatches most of us wear.
This would be a nice opening for wearable companies. More people than ever want to protect themselves from UV exposure. A wearable that tracks it and puts it into context could be a really useful tool.
Is the Gem for everyone? No. It costs $249 at full price, which is steep for a single-purpose gadget. Its vitamin D figures are estimated from your light, skin type, and exposure. And no app replaces sunscreen, shade, or common sense. The90 itself says the Gem “does not replace sunscreen.”
Plenty of people don’t need a dedicated UV exposure tracker. Still, making everyday UV exposure harder to ignore is worthwhile. As someone who already wears a tracker all day, I’d like to see this feature on my wrist.