[Update: May 2022] How to trick the heart rate monitor on your fitness tracker (NSC edition)

Disclaimer: The following information provided is for educational and experimentation purposes.

Recently I've seen a spike in interest over this topic based on Google search results. Hence I will give a quick summary on the latest garbage trackers given free to participants of the steps challenge.

Testing performed on AXTRO FIT (Season 4) & Axtro Fit 3 (Season 6)
Final results and conclusion:
Certain clear or reflective surfaces may induce trackers to record MVPA values, surprisingly consistently. Steps count sensitive to vibratory effects from simple rotary mechanisms such as fan motor will work.