What if you could zap your brain into a state of calm or energy with only the push of a button?

It may sound like the stuff of sci-fi, but it's now the promise of a new class of tech wearables created by teams of Silicon Valley entrepreneurs and neuroscientists.

Several devices have come onto the market claiming to use brain stimulation to alter an individual's mental state. One of the latest is Thync Vibes ($299), a stick-on device that delivers low-grade electrical pulses ("vibes") into the scalp to cause a change in automatic nervous system activity.

How does it actually work?

Those who are brave enough to try it will stick a small triangular device onto the side of the forehead and attach another small strip to the back of the neck or behind the ear. Using the Thync iPhone app, you adjust the intensity and duration of the session, which can range from 5 to 20 minutes. During that time, pulses of electricity will activate either your parasympathetic nervous system (the "rest and digest" system, which slows the heart rate) or your sympathetic nervous system (responsible for the "fight or flight" response), depending on whether you choose the "calm" or "energy" setting.