There’s no arguing that they’re popular—here's what we do and don't know about how accurate they are.

By Samantha Zabell
Updated September 09, 2014
Credit: Christopher Ames/Getty Images

After months of rumors, Apple finally announced its highly anticipated Apple Watch on Tuesday. Among its multitude of functions (one of the weirder ones being the ability to “share your heartbeat” with a friend) CEO Tim Cook called this customizable watch a “comprehensive health and fitness device,” at the Apple Live event.

The watch-turned-fitness tracker monitors a host of health-related metrics, including distance, intensity, and total body movement. The gadget promises to let you set calorie-burn goals, and track your activity levels and standing time—important given how sedentary jobs can adversely affect your health. With its “workout” feature, you can create benchmarks based on time, calories, or distance, and sync the data to the iPhone’s fitness and health apps for more features.

While the Apple Watch offers a myriad of features, when it comes to being a wearable fitness tracker, it’s hardly the first on the block. It joins the likes of the Fitbit, Jawbone, and (despite discontinuation rumors) the Nike FuelBand, which already adorn arms and clothing to track exercise progress, sleep patterns, and other health behaviors, all with the goal of motivating you to stay healthy. In a 2013 Pew Research Center survey, 21 percent of adults said they used technology to track their health, and the market research company NPD Group reports that wearable technology market revenues have totaled $96 million since October 2013. But the real question is: How well do they work?

The research is mixed as to the effectiveness of various wearable fitness trackers on the market so far—a 2013 study found that trackers mounted on shoes monitored movement far more efficiently than those at hip-level. Similarly, a 2014 study at Iowa State University found fitness trackers could be inaccurate when it came to measuring calories burned. Those researchers tested eight different models, and showed that error ratings ranged from 9 percent to a more startling 23.5 percent, which could have a real impact on achieving health goals.

But if you’re not using the tracker for the data, and rather just as a motivational tool, those findings might not matter as much. A simple pedometer seems to be effective at just getting people to move, regardless of calories burned or other personal health measurements. When the pedometer became popular, a 2007 Stanford University doctor reviewed 26 studies that involved the assessment of pedometer use to determine its effectiveness as a fitness motivator. After the analysis, researchers concluded that the tool did, in fact, increase physical activity among wearers, and was also associated with significant decreases in BMI and blood pressure. And a 2008 study by researchers at University of Michigan Health System found that pedometer-based walking programs resulted in a consistent pattern of weight loss. Not to mention that it’s a much cheaper investment—the most basic pedometers can cost less than $10, while the more complex activity trackers can be more than $100.

So bottom line? While some trackers are more accurate than others, the data might not be airtight. But if it helps you stay motivated toward healthy behaviors, that’s never a bad thing.

Then again, Apple’s new watch doesn’t come out until next year—maybe they finally got the technology right. Will you be buying one?