pedometer
A pedometer is a simple device that measures distance by counting the number of steps you take. It does this by detecting a jolt or shake as each foot hits the ground.
Pedometers are inexpensive (often less than $20) but not all that accurate. They rely on an average stride length to calculate the approximate distance you've covered. They're also susceptible to missing or counting extra steps as a result of normal variations in your body's motion.
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