I use a TENS unit with an almost identical setup to the paper (ear clip is the same, duration is the same, frequency is 30hz instead of 25hz).

My use of vagus stimulation is for managing anxiety and promoting digestion / gut motility. I have neck issues that probably impinge on this nerve, contributing to these symptoms. Evidence suggests that the effect isn't purely psychosomatic; when laying on my back with TENS, I observe an increased frequency of GI tract "gurgles" relative to off. The observable product of my GI tract has also normalized somewhat.