See the Unseen UV
A smart phone case with built-in UV sensors and photochromic 'ghost' patterns that appear in sunlight, paired with an app using facial mapping to show exactly where you've missed sunscreen.
You point your phone at your face after a day at the beach and see glowing 'ghost' spots exactly where you missed sunscreen.
Your nose, left cheek, and hairline are lit up in eerie purple, while the phone case itself has developed intricate ghostly patterns just from being in the sun.
Making invisible UV rays suddenly visible and undeniable.