Albert Sun in The New York Times:
For years, health advocates have been telling us to move more. But just how much more? A multitude of activity tracking devices now promise to answer that question. Generally, these digital monitors, which can be worn around the wrist, on collars and belts, even as jewelry, record how and how much you move throughout the day. Some aim to do a great deal more. Makers of the devices have begun intensive campaigns aimed at convincing the large population of “worried well” consumers to get wired and start recording their every move. How well do these work? Curious about the benefits and limits, I’ve been testing as many different models as possible — wearing them day and night for six months, 11 models in all, sometimes four at once. I’ve learned a great deal about these gadgets. And about myself.
I’d thought I was a fairly active person: I bike to work most days and hit the gym or get other physical activity two or three times a week. The trackers, on the other hand, showed that aside from those spates of exercise, for the vast majority of each day I was completely sedentary. But that may not be the whole story. Activity trackers typically combine a wearable device with a website or smartphone app to view data collected about your movements. The goal is to measure not only your steps from the parking lot to your desk, but also your sedentary down time at work or in front of a television, bursts of intense exercise and even your sleep habits — all to create a complete picture of your most and least healthful behaviors. Some models also offer tips and set goals based on your data.