More than anything, I’m surprised it’s a square.

A square with rounded corners, Nest CEO Tony Fadell corrects me. Then the man responsible for the iPod and the Nest thermostat beams at me and delivers the line for his newest product. “Safety,” he says, “shouldn’t be annoying.”

He hits the large circular button on the rounded square in front of us. “Heads up!” it says in a calm female voice. “There’s smoke in the kitchen.”

This is the Nest Protect, a $129 smoke and carbon monoxide detector. Instead of simply beeping, it tells you exactly what and where the problem is, and you shut it up just by waving at it. It will last for years on six AA batteries, and ping your smartphone when they need to be replaced. And it serves as an activity sensor for the Nest Learning Thermostat, letting it more accurately adjust your heating and cooling as it learns when you’re home and away. It is ridiculously expensive — Amazon’s best-selling smoke detector costs $31 — and oddly beautiful. Particularly the black one, which dramatically sets off the multicolor LED ring around the button and lends a touch of ‘80s flair to Nest’s logo.

“We’re about reinventing unloved categories,” says Fadell. He can’t stop smiling as he shows the Protect to me. I’ve come to know that smile in the past two years. It’s how Tony looks when he feels like he’s made a winning bet.