Phone-based augmented reality has started regularly showing up on apps like Snapchat, YouTube, and, of course, Pokémon Go. And virtual reality has found a reliable niche in gaming, film festivals, and arcades. Augmented reality glasses, meanwhile, are a rare sight in everyday life, but they hold an outsized place in our imagination. And in many ways, they’re the most exciting and scary of these three technologies.

AR glasses promise to untether us from our increasingly hated phones. Google co-founder Sergey Brin once claimed that smartphones were an “emasculating” and isolating “nervous habit,” while products like Google’s Glass headset offered the promise of freedom and connection. The “everyday smart glasses” startup North calls them a way to stay “centered in the real world.” Idealistic and well-funded startup Magic Leap offers a vision of AR glasses uniting the world on a new kind of tech platform.

On the other hand, science fiction has warned us about AR encroaching on the real world. My colleague Nick Statt has written about how Facebook-built AR glasses could produce “aggressive advertising overlaid over every inch of our line of sight, and the kinds of public ranking systems that split society into the haves and have-nots.” And that’s not even touching the question of surveillance, which led some bars and restaurants to outright ban Google Glass and could only get scarier as facial recognition technology spreads.

AR headsets haven’t made the jump to consumers, but they’re still a full-fledged industry. It’s similar to the way VR was used in research and simulations through the ‘90s and ‘00s, well before the Oculus Rift. It turns out that when you actually have a reason to use AR glasses, they’re great. They’re just not anywhere near replacing our phones.