Last September, in The British Journal of Sports Medicine, Australian researchers published a review of studies that compared subjective and objective measures of “athlete well-being” during training. The objective measures included state-of-the-art monitoring of heart rate, blood, hormones and more; the subjective measure boiled down to asking the athletes how they felt. The results were striking: The researchers found that as the athletes worked out, their own perception registered changes in training stress with “superior sensitivity and consistency” to the high tech measures.

Outsourcing your self-monitoring to a gadget may have another downside. Steve Magness, a track coach at the University of Houston, recently drew on arguments from Matthew Crawford’s book “The World Beyond Your Head” to argue that running with a GPS watch “slackens the bond between perception and action.” In other words, when you’re running, instead of speeding up or slowing down based on immediate and intuitive feedback from your body and environment, you’re inserting an unwieldy extra cognitive step that relies on checking your device as you go.

None of this adds up to a case that wearable fitness technology is a waste of time. For many people, the primary purpose of an activity tracker like a Fitbit is motivation. Simply knowing how many steps you take, or how much sleep you get, will spur you to seek more, especially if you’re comparing and competing with your online peers — a big difference from the un-networked $2 pedometers that came in cereal boxes a decade ago.

There’s reasonable evidence that this approach has useful effects, at least in the short term. In one study using activity trackers published in February, participants increased their daily step count by 970 after six weeks, an amount that previous studies have linked to improvements in body mass index and insulin sensitivity. Even if it’s true that more than half of users eventually stop wearing their devices, it’s still a laudable outcome that several million people exercised more than they otherwise would have for a year or two.

Ultimately, it is those aggregate numbers that offer the most exciting possibilities: The collective data stream from our devices amounts to by far the largest and most comprehensive observational health trial ever conducted. We have the data; now we just need to figure out what it means.

Technology companies are already taking the first steps. Rather than simply tracking your individual heart rate, calories burned and so on, they want to use that flood of data to enable us to make more informed decisions. Under Armour, for example, just announced a partnership with IBM to provide “cognitive coaching” that will crunch all your tracked data, and compare it to data from millions of others like you, in order to offer smarter advice on how to exercise, eat and sleep. Other wearable companies are pursuing similar projects.