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.