Manny Fiori’s job is to make sure your phone doesn’t kill you. He guards the entrance to a garage near my San Francisco office and stops cars from hitting pedestrians so engrossed in screens they don’t notice they’re stepping into traffic.

“People are so oblivious nowadays,” says Mr. Fiori, a building employee who barks orders and even holds out his arms to stop both cars and people.

Watching the morning rush from his driveway is a scary measure of our smartphone addiction. In one hour last week, we tallied 70 pedestrians who never looked up—some watching TV shows, many grimacing while pounding out emails. Five of them can thank Mr. Fiori for preventing them from colliding into cars.

I’m hardly innocent. My phone bears scars that look like I got in a fight with a bobcat—actually, I walked into a wall while texting.

It was sort of a joke when the distracted pedestrian phenomenon first arrived, right? YouTube is filled with highlight reels of texters falling into fountains. The Germans have a word for such people: smombie—smartphone plus zombie.

But as we reach a point where garages have to hire guards to save us from ourselves, texting while walking is no longer a joke.

It’s a public safety conundrum, and a symptom of an addiction. At the very least, it’s a design failure in smartphones that have mastered how—but not when—to get our attention. It’s time to ask what responsibility the tech industry has to address the problem.

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