High tech sunglasses

Nowadays when you're laying on the beach in the sun, maybe after taking a short bath. You always see people with sunglasses! You even see people with sunglasses on the street! They have gotten so popular nowadays. But I totally understand that, they do look pretty cool! I myself got a pair of sunglasses which I like to put on sometimes. But I recently heard of something called a optical shutter. It's like automatic sunglasses. They get black when they're it contact with light. Isn't that amazing? Imaging having one of those at the beach!