L'Oreal introduced a new wearable UV sensor today that you can stick on your nail. It's truly just a sensor; it doesn't pair over Bluetooth or Wi-Fi to your phone. Instead, it's NFC-enabled so you can scan it with your phone to retrieve the UV data it's collected. It should work with both Android and iOS. The UV Sense, as the company calls it, is meant to help people track how much time they spend in the sun without being overbearing. The nail sticker is a statement, but not a massive one.
The UV Sense will determine long you've been outside, and once synced with your app, provides a score that says whether you're spending too much time in the sun. The amount of sun everyone can handle varies, L'Oreal tells me, so it'll ask you some initial questions about your skin tone to set a baseline. Of course, the app also recommends products based off your skin score. It'll suggest its own products along with more general advice.
The sensor comes with replaceable adhesives, so you can rewear it, although you can snap it onto other items, like a watch or sunglasses.
The UV Sense will be available in the summer for an undisclosed price, although a spokesperson tells me it'll be under $50.