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The Watch RK Prime 29 Onlinemirror wakes up suddenly, one glowing blue-white circle appearing like the eye of Sauron on its thick black bezel. A red laser beam shoots out, hitting its mark on the Bluetooth-connected platform where the mirror's designated owner is to stand.

"Phone down, step up!" says a cheery-faced app. The man, who was previously told to shed his clothes, obeys, assumes the position -- back straight, fists clenched -- and is slowly spun around like a human rotisserie.

Minutes later, there's an on-screen 3D clone, identical to the human in every detail except for its dead eyes and gray-goo skin.

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This could be the opening scene of a chilling Black Mirrorepisode. It's also a fair description of what happened when I tested a literal black mirror, the Naked, which a startup called Naked Labs is touting as the world's first in-home 3D body scanner.

The company's aim isn't just to transform your fitness regimen by giving you more information on your body than you could ever want. In the long run it also hopes to help you buy clothes, to aid in the production of furniture tailored to your body, and even to provide a perfectly lifelike avatar for video games. (The company just announced a $14 million series A funding round to help realize these many visions.)

I found myself eating more salads and lacing up my running shoes

I've been eagerly awaiting the arrival of the Naked, creepy name aside, since I tried out a prototype back in 2016. Using three Intel RealSense depth sensors, it bounces light off your body at all angles while simultaneously weighing you. Collecting around 4GB of data per scan, the mirror's onboard computer compresses that into a 4MB model for your Naked app that is accurate to within a tenth of an inch -- plus a body fat percentage number that's way more accurate than any bathroom scales.

So when a review unit showed up at my door, I was both eager and terrified to try it. After three days of unflinchingly realistic scans, able for the first time to really see what I look like from all angles, I found myself eating more salads and lacing up my running shoes more frequently than normal. Though some of the most promising planned features aren't on the app just yet, this is already a highly effective smart mirror -- the "scared straight" of home fitness. But at what cost?

Original image has been replaced. Credit: Mashable

Back in 2016, early adopters were able to order a Naked for $499. The final device, we were told, would be priced at $999. But the tech and manufacturing proved more challenging than expected, and the Naked is on sale as of Wednesday for $1,395 with delivery expected in the fall. That price, substantially more than the average year of gym membership, puts this device squarely in the realm of Tesla customers and other well-to-do gadget freaks.

Conforming to this stereotype, one of its early customer videos is about a dude who moved to Silicon Valley and started powerlifting:

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That said, if you're serious about getting in shape, the price tag could be worth it. The main promise of that gray 3D avatar is it can show you how your body is changing over time, telling a story that the dry numbers often miss.

Many of us have had the experience of trying a new diet or workout regimen that we thinkis working, but the scales don't agree. Often that's because muscle is more dense than fat; gain one and lose the other, and your weight will plateau, or even go up. But even when the raw numbers do show a difference, it can be dishearteningly small -- whereas a body scan will tell a completely different story.

For example, Naked Labs shared (with consent) this result from one of their 50 beta testers who was training for an Ironman triathlon. Between February and July, she put in a ton of workouts, but only lost 3.2 pounds and 2.4 percent body fat for her troubles.

If you look at the app screen that shows her scans side by side, however, there's little doubt this budding triathlete became substantially more fit.

Original image has been replaced. Credit: Mashable

Of course, you don't get to see this kind of change in your early scans. All you have is a nude gray version of your body that you can rotate with your finger, finally seeing what the world has seen for decades -- what you look like from behind. (Feeling shy about your nether regions? The Naked allows you to wear underwear and a sports bra, although dark underwear can absorb light and will sometimes throw off the scanner.)

Because the app provides your fat mass and lean mass, you can tell if your weight loss has come at the expense of muscle or gut. It also gives precise measurements for your shoulders, chest, left and right arms (it's always fun to find out which is longer), waist, stomach, hips, upper thighs, lower thighs, and calves.

Unless you're a bodybuilder, that may be a dizzying and unnecessary amount of information. In the coming months, Naked plans to add a "heat map" to the app that will show you precisely where on your body muscle and fat are being added or lost. On the principle that images are more motivational than numbers, this seems like it will be far more effective than the current set-up.

Similarly, another feature to be implemented in the next six to eight months will show you how you would look if you lost 10 pounds, say, which seems like the best possible way to make you want to skip dessert. In the long run, Naked has tentative plans to start telling you what sort of sport your body will be most suited for -- do you have the lithe limbs of a gymnast or the power thighs of a world-class cyclist?

Original image has been replaced. Credit: Mashable

The company also plans to announce a partnership with a clothing manufacturer that will use your body data -- which is only ever shared with your consent -- to find your perfect outfit. The low-hanging fruit of clothes, Naked CEO Farhad Farahbakhshian told me, are shirts and skirts. Pants and jeans may take a while longer to fit to your scan. (Farahbakhshian, who according to his scans has just 6 percent body fat, also says he's currently using his scan as his avatar in the video game Fallout 4.)

In short, early Naked purchasers will be getting in on the ground floor of something that could be huge. I'm encouraged enough by my early experience with the Naked that I will keep testing it; watch this space for a full report after one month, diet and weight-training included.

I'm still a little afraid of the fact that I've invited a literal black mirror into my bedroom; however, this may yet be one futuristic tech tale with a happy ending.

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