Silicon Valley-based Thync produce a "pod" that affixes to the user's lower neck. Using transcutaneous electrical nerve stimulation (TENS), the pod promises to decrease anxiety and help induces sleep.
They appear to have at least one peer-reviewed article on the system's efficacy.
From their own material,
In one internal study 109 subjects were blindly given real and placebo programs. Using a custom stress survey an overwhelming 88 subjects rated the real program as being more effective than placebo compared to only 9 people who rated the sham higher (P = 1.74 X 10-20).