For anecdotal data, I'm a big fan of Apollo Neuro. It's a small band worn on the wrist or ankle and vibrates to stimulate the vagus nerve. Similar effect to tapping on your wrist. The sleep mode seems to improve my deep sleep scores on my Oura ring. I haven't done any proper data analysis to confirm.
Correct, the vagus nerve itself doesn't extend into wrists and legs AFAIK, but other nerves connect to it. Wrist tapping and acupuncture stimulation of points on the wrists are quite common. I'm assuming devices like Apollo Neuro target a similar effect on those pressure points on wrist and ankles.
Here's a random article about vagus nerve and acupuncture [1]. I'm not sure about actual pubmed type studies. On a personal level, I think these devices are well worth giving a try. Just pick one with a good return policy if it doesn't work for you.
Apollo Neuro claims to have lab data proving efficacy: https://apolloneuro.com/pages/science
Even if it's more of a placebo effect, I still enjoy the benefits of devices like this.