What an awesome invention! The studies about the vagus nerve are spot on, there are also some stimulators that get clipped to the ear and there are trials going on for kids with autism to see if it helps them with anxiety. I think that it is marvellous that we live in a century where so many cool stuff get to be invented for the well being of the human individual.
The breath is important I think that taking long breaths and then exhaling slowly helps, I try it once in a while too, it helps