Garmin 010-12520-00 Running Dynamics Pod

Running Dynamics Pod
Computes and Transmits Meaningful Data
Computes and sends 6 running dynamics metrics to your compatible device
Battery life: replaceable battery lasts up to 1 year (assuming 1 hour daily use)
Automatically turns itself on and off
Tiny size: at less than 0.5 ounces, you’ll forget it’s there
Compatible devices connect with the Garmin Connect Mobile app to automatically sync your data and connect with others

How It Works
The Running Dynamics Pod has an accelerometer in the module that measures torso movement to calculate these 6 running metrics:

Cadence is the number of steps per minute. It displays the total steps (right and left combined).
Ground contact time balance displays the left/right balance of your ground contact time while running. It displays a percentage. For example, 53.2 with an arrow pointing left or right.
Stride length is the length of your stride from 1 footfall to the next. It is measured in meters.
Vertical oscillation is your bounce while running. It displays the vertical motion of your torso, measured in centimeters for each step.
Vertical ratio is the ratio of vertical oscillation to stride length. It displays a percentage. A lower number typically indicates better running form.
Ground contact time is the amount of time in each step that you spend on the ground while running. It is measured in milliseconds.