Custom-designed hardware rules.

DIY attempts at electrical brain stimulation to improve cognition are to get easier. Nature editorial.

He uses non-invasive stimulation to phase cancel the tremor.   The stimulation mirrors but is opposite phase of the motor cortex oscillation.  Reduces tremor by ~40%  Brittain et al 2013

It was recently reported that low-voltage, non-invasive brain stimulation improves mathematical abilities.  Does it?  Here’s a cautionary discussion:
Does Brain Stimulation Make You Better at Maths?

The title says it all.  Oscillations are useful for all sorts of things.
Synchrony in 32 metronomes