UV Sense is a big leap from L'Oreal's last offering, My UV Patch, which was just a sticker loaded with a series of dyes. These dyes changed color depending on how long they've been exposed to light, and users could track the changes by taking pictures with the corresponding app. This time around, the sensor is designed to be worn more than once, and will store up to three months' worth of data at a time.

Would-be owners can affix the sensor to their thumbnail -- where, apparently, you get optimal sunlight exposure -- for up to two weeks. They'll later need to re-apply it with a fresh adhesive patch, several of which come included in the box.

UV Sense needs an iOS or Android device with NFC, since you'll need to tap your handset on the sensor to transfer data. From there, the companion app will tell you about your risks to ultraviolet exposure and will suggest better habits, including when to get out of the sun and the best time to reapply lotion.

L'Oreal is working with MC10, a medical technology wearables outfit established by professor John Rogers at Northwestern University. Rogers is famous for developing the "wearable tattoo," circuit boards no thicker than a band-aid that attach to people's skin. The eventual goal for such technology is that it will replace the bulky and invasive monitors strapped onto hospital patients.

The fact that the device is so small, and yet is packing a flexible circuit board, capacitor and an LED within its tiny frame is encouraging. After all, if the partnership can solve the issues of power and transmission, then it's possible that future devices in this range will be more autonomous. That should dramatically reduce the sort of bulk that hospitals normally invest in, and make patients' lives a little bit easier.

If you're interested in testing UV Sense, it will be available this summer in the US for an as-yet unspecified price. A global roll-out will follow in 2019, while the My UV Patch will also be made available through the Laroche website.

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