Getting and staying fit can be a tough endeavor. Junk food is tempting, working out is exhausting, and at the end of the day, the bathroom mirror never seems to reflect much of a difference.

Mirrors, like other methods of tracking fitness like weight and BMI, can be misleading. Looking at your body on the outside can’t track the changes happening inside, and a number on the scale doesn't calculate muscle mass. Body fat measurement is a much more accurate way to assess fitness, but most people don’t have the tools necessary for this lying around the house. The Naked 3D Fitness Tracker, now on pre-sale for $499, is in a position to change that.

The system, designed by Silicon Valley startup Naked Labs, is essentially a magic mirror that calculates and computes body fat and muscle data people can use to track body changes over time. “Our users have loved being able to see their bodies’ changes,” Naked Labs founder and CEO Farhad Farahbakhshian told Mashable.

The company has been conducting beta-testing with real people since 2015. So far, testers report that the app’s time-lapse feature, where they can actually see their body changing over days and weeks, has kept them on track. Farahbakhshian said the system isn’t only for those who want to build muscle or lose fat, though.

“We have even tracked pregnancies month by month with some of our beta users so that they could see how pregnancy changed their bodies,” he said.

For all it can do, the scan is relatively simple. According to Mashable, there are no buttons and no readout screens; users know where to stand because of a laser pointer in the mirror, a circle lights up, and that’s it. Everything else is contained in the app, which will be available for both iOS and Android. Farahbakhshian said he also expects the system will be compatible with Fitbit, Apple Health, and other fitness tracking systems when it becomes available.

Unlike weighing yourself or calculating BMI, the Naked tracker is as accurate as the water displacement test for body fat — this means it can calculate body fat percentage with 1.5 percent accuracy. Though the almost $500 price tag is nothing to scoff at, it’s actually reasonable for those committed to tracking their fitness. A national survey found that 49 percent of Americans said they would like to lose weight, with 24 percent saying that they were “seriously trying to lose weight.”

Those people will just have to wait for Naked’s magic mirror, though, since the systems won’t be shipping until March 2017.