One of the first products I looked into as helping mitigate harmful EMF was the Q-Link pendant - which works on what they term Sympathetic Resonance Technology. Below is some of what I found. I also heard from someone using the pendant that while wearing it, muscle testing (which seems kinda new age to me) did not work.
See also:
https://pubmed.ncbi.nlm.nih.gov/12614535/
https://www.shopqlink.com/pages/sympath ... -resonance