ETS Breathing Necklace
https://www.frontiersin.org/articles/10.3389/fpsyt.2018.00044/full
https://sass.uottawa.ca/sites/sass.uottawa.ca/files/how_to_stimulate_your_vagus_nerve_for_better_mental_health_1.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6189422/
https://www.psychologytoday.com/us/blog/the-athletes-way/201905/longer-exhalations-are-easy-way-hack-your-vagus-nerve
https://www.health.harvard.edu/staying-healthy/understanding-the-stress-response
https://www.neuropeakpro.com/does-deep-breathing-really-do-anything/