Fitness trackers use suites of sensors and algorithms to turn data from your training regimen into (hopefully) meaningful information about how race-ready you are. But for the rest of the time—when you’re sitting at a desk—there’s not much for devices to do. Spire, a clip-on tracker that looks like a small, silvery stone, monitors a more subtle aspect of your physiology: your breath. By measuring the small vibrations and abdominal movements caused by inhaling and exhaling, Spire’s analytics software can determine how stressed or focused you are, the company says. If you haven’t taken a deep breath in a while, Spire’s smartphone app will kindly remind you. It will even guide you through a calming exercise.


Price: $150

Battery life: Seven days

Charging: Qi wireless

How are breath and emotion connected?

Vagal Tone: The term refers to activity of the vagus nerve—a cranial nerve that originates in the brain stem and connects with and regulates the resting states of many of the body’s organs, including the heart. Since vagal tone cannot be measured directly, researchers assess other biological processes, such as respiratory sinus arrhythmia, or changes in heart rate during a breathing cycle. During stressful situations, heart rate varies more wildly.

This article originally appeared in the September 2014 issue of Popular Science.