Measuring your personal UV light exposure hasn’t historically been easy, as UV sensors aren’t built into typical wearables, smartphones, or other items people tend to carry around outside. That’s about to change thanks to L’Oréal, which today announced availability of My Skin Track UV — a wearable accessory that gathers personal UV exposure data to share with Android phones and iPhones, notably without requiring either Bluetooth or a battery.

With its components inside a circular, shirt button-sized housing, My Skin Track UV will typically be clipped to a shirt in a position where it can measure both UVA and UVB rays. The sensor can also be worn on a necklace chain, assuming it stays exposed to sunlight. Jawbone designer Yves Behar created the fashion-neutral and waterproof white, blue, and silver enclosure, which measures 12mm wide by 6mm high — mostly in the largely hidden clip.

L’Oréal’s most impressive feat: The tiny sensor can store up to three months of UV data at a time, as well as transfer it to your phone, without requiring its own battery. An LED inside is powered by sunlight and uses NFC to share data, requiring only a tap to your phone to initiate a transfer. UV data is notably compatible with Apple’s Health app and enables you to determine your current percentage of maximum sun exposure.

Rather than leaving the sensor to do all the work, L’Oréal includes a companion app that uses your phone to display real-time data on other environmental factors such as pollution, pollen, heat, and humidity. Like many free weather apps, this app rates the overall air quality level, provides a pollen count, and offers current weather details, but it also includes personalized skin advice specific to all of the gathered UV and ambient data.

My Skin Track UV is debuting as an Apple Store exclusive today for $60 in the United States, and is available both online and in select retail stores. Its companion app is free from the App Store and Google Play Store.