You wear them on your wrist, around your torso, attached to your shoe or on your arm.
'Wearable' tracker devices are the hottest products on the exercise market. It may be the motivation you need to keep moving and it's objectivity won't fudge the numbers. It provides an honest assessment of your workout and/or how much physical activity you have accumulated during the day.
Via Larisa Ens, Kirk Fontaine