The best place to wear it is on your hand, since you can pretty much guarantee the sun will be hitting that area whenever you're outdoors (and what a good reminder to apply SPF everywhere), but we dare you to slap it on your cheeks if you want to measure how much exposure your face is getting during a day at the beach.Eager to snag your own My UV Patch? It'll be available on La Roche-Posay's site beginning July 18 and at select physicians' offices across the country (kill two birds with a mole check while you're there), and it's free, which makes protecting your skin that much more accessible.But beyond the patch itself — which is totally cool — what we're really excited about is what the technology behind it could mean for the future of preventative skin care. Imagine being able to track your skin's pollution exposure, hydration levels, reparative quality...all through a sticker and a smartphone. It might just convince us to put down the wine, go to bed earlier, and move out of NYC. Well, maybe not that first one.