In business and in fitness, it's a truism that you get the results you measure for. As a spinning instructor at San Francisco's Bay Club, Farhad Farahbakhshian saw what happened when exercisers made the mistake of believing what the number on the scale was telling them. People who were gaining muscle and losing fat would see their weight unchanged or rising, get discouraged, and abandon their workout programs. 

Unlike most spin teachers, Farahbakshian is also an experienced electrical engineer. He says he put his mind to coming up with "a way of visualizing progress far better than what you can see from a scale or a mirror." 

The solution he invented,  Naked, bills itself as "the world's first 3D fitness tracker." A Naked unit consists of two connected components: a digital scale with a built-in turntable and a full-length mirror lined with infrared sensors like the ones in a Microsoft Kinect gaming console. As you stand on the scale, the turntable rotates, allowing the sensors to capture a detailed 3D image of your body. Since fat and muscle have different densities, knowing the fluctuations in your volume and mass over time allows Naked to extrapolate how your body composition has changed. A heat map view in the Naked mobile app shows where those changes happened--a 2 percent gain in upper body muscle, for instance. Another view shows asymmetries, an important factor in predicting injuries. You can also scroll through a virtual slideshow of 3D "selfies" for a time-lapse view of how your body's appearance has shifted.  (This video offers an idea of how it all works.) 

While it's also possible to measure body composition through "bioimpedance," which involves running electrical current through the body, Farahbakshian says his method has a substantially lower margin of error of +/- 2.5 percent versus 8 percent. "It's actually a very computationally intensive task to create a 3D body model," he says. "This is probably the smartest device you'll have in your home." 

Backed by NEA and Three Leaf Ventures, Naked Labs starts taking preorders today. At $499, the device will be pricey, but Farahbakshian notes that the mirror is extra thick and warp-free while the scale, unlike most scales, works on carpet. Preorders won't ship until March 2017; the company is waiting to see how many preorders it books before selecting a manufacturer. Farahbakshian plans to use the time in between to further hone the accuracy of the scans. (A demo unit I tried out captured an uncannily accurate image of my clothed body and face, but had trouble rendering my hair, a bug Farahbakshian says is still being worked out.) 

Longer term, he hopes Naked will become a platform for personal trainers and integrate with other fitness apps and trackers. The possibilities don't stop there. An in-home 3D body scanner would be useful for everything from remote medical diagnoses to ordering custom clothing. Farahbakshian is aware of the opportunities--but first, he says, his goal is to give people a reason to stick to their workout goals.