The phrase is due to William Gibson in his novel Spook Country, where artists use WiFi and GPS and VR goggles to create a new kind of art: virtual installations ghosted over the real world. Slip on the glasses and see River Pheonix’s body lying on the sidewalk on LA, or a giant squid hovering over Tokyo. Cyberspace begins to reach out to us, becomes “outside” instead of “inside.”

The thing is, you could do this now with an iPhone.

Here’s the plan: use the GPS to get an approximate fix, down to a few meters. Then look out through the camera to get a shot of the environment. Match this against data from Google Street View to recover precise camera position and orientation — the algorithms already exist. Composite in the ghosts, and display the result on the screen. The iPhone is now a window into cyberspace.

You could use it to visualize reviews tagged to store windows. Watch data packets fly between cell towers. Follow a line on the sidewalk to your destination. Remind yourself of people’s names. Or, of course, for art. Imagine a real-time version of the strangely delightful Death Star over San Francisco.

Of course, there are problems. The iPhone doesn’t have the processing power to do this in real-time, so you’d be limited to snapshots on current hardware, a ghostly camera instead of a camcorder. Google Street View is also copyrighted data, an expensive and proprietary data set (not to mention controversial) and it’s not clear how they’d react to such novel uses. But our phones are becoming ever-more powerful, and open maps are inevitable (either wiki-style, as in OpenStreetMap, or through data mining, as Photo Tourism does with Flickr.) The pieces of a personal cyberworld viewing device already exist, and they’re getting faster and cheaper.

And of course, as soon as they’re fast and cheap enough, we’ll start to get used to the idea of seeing the world through an image-processed lens. We’ll instantly find new things to do with it; the old McLuhan/Gibson/Banks notion of externalized perception and cognition will suddenly become solidly mainstream and consumer.

I’m here to tell you it’s not long now.