I have used the Gammacore for the last month and it works great as a preventative treatment for me, I use it for 4 minutes twice a day.
I paid $598 for the gammacore device that has 300 two minute sessions and a 30 day shutoff timer that shuts off the device after 30 days of use (or non-use.)
Once activated the gammacore expires in 30 days, I used it 90 times in a month so 300 uses is more than enough for anyone in a month.
I also underwent Botox for a year prior but the side effects of Botox were too much for me so I prefer the gammacore.
I am a retired Electrical Electrical Engineer that served on a nuclear submarine so I know a little about acoustical energy, I took the gammacore apart and the 2 silver round electrodes on top are actually sonic transducers that emit sound waves - NOT electrical waves. Underneath the electrodes are two clear plastic balls filled with a gel in which the sound wave is transmitted into the vagus nerve. 2 electrode screws are inserted into the gel to transmit the sound energy and the frequency is adjustable.
This stimulation of the vagus nerve is by sound, quite similar to the Yoga chant "oooohhhhmmmm" that also can vibrate the vagus nerve slightly while the gammacore can REALLY vibrate the vagus nerve!
The Gammacore is powered by 2 three volt batteries in parallel so if you know what you are doing you can "bypass" the 30 day shutoff timer and use the single gammacore for months and save thousands. You will need a couple electrical jumpers and a small rheostat to adjust the sound frequency, can get at radioshack for $5 bucks.
I will post the detailed instructions and photos as to how to bypass the gammacore timer and have a permanent device, I cannot recommend this for novices due to safety risks and always wear eye protection when working around batteries.
And I predict gammacore will start selling a permanent gammacore device soon, $598 a month is ABSURD!