Tracking breathing

From Faster Than 20

There are several ways to monitor breathing. The technique I'm highest on (for augmented facilitation) is via sensors that measure abdominal / chest movement, such as Spire.

Another technique is by measuring heart rate variability (HRV), which corresponds to inhaling and exhaling. The Apple Watch, Fitbit's Charge 2 and Alta HR, and the Garmin Vivosmart 3 all measure respiratory rate this way (although only Garmin tracks respiratory rate in the form of is "stress" measure).

Many of these devices offer mindfulness features that track your respiratory rate over time and suggests pauses for deep breathing.