ELI5 Activity Trackers - how do they detect deep sleep?

What are the creative ways people fool their FitBit? How does my activity tracker differentiate between steps and my tapping to a rhythm? Does it use GPS to calibrate? How does it know what stage of sleep I'm in? ... We explain like i'm five! Help more people fund us by leaving a rating on iTunes. Thank you to the r/explainlikeimfive community, and specifically the following reddit users whose questions and responses formed the basis of this conversation: failtuna, fieldpeter, devilishgainz, srslylovesgames & groundhogcakeday To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Twitter: or send us an e-mail: ELI5ThePodcast@gmail.com

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ELI5 Activity Trackers - how do they detect deep sleep? is an episode from Explain Like I'm 5: Bite sized answers to stuff you should know about - in a mini podcast by ELI5 Explain Like I'm Five Podcast.

This episode is 8:24 long.

This episode was published on Jan 23, 2026.

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