A portable tracker continuously detects body movements on a 3-axis accelerometer. The data is recorded as long as it is used and turned on, allowing the tracker to track if the person is walking forward, running fast, or even if they are still.
The Fitbit Charge 5 is among the most accurate for measuring steps and heart rate (although accuracy isn't everything). By Jane McGuire published 1 June 22 Looking for something with more features? The Garmin Venu 2 plus has 25 different training modes and all the race tracking features you expect from Garmin, plus the ability to store up to 650 songs on your watch, make and answer calls from your wrist, and invoke Siri or Google Assistant.
Your smartwatch or fitness tracker will have an accelerometer installed and this will track your activity level every day. The data collected by the accelerometer will be used by the algorithm when calculating the amount of calories burned.