Fred Ehrsam, billionaire co-founder of Coinbase, is shifting his next big bet from cryptocurrency to the human brain, unveiling a non-invasive brain-computer interface designed to modulate brain activity with sound waves.

Ehrsam’s entry as the latest competitor to join the race to develop accessible brain-computer interfaces (BCIs) follows similar recent efforts from tech leaders like Elon Musk, Jeff Bezos, and Bill Gates.

On April 8, Ehrsam’s startup, Nudge, unveiled its first product, the Nudge Zero. A noninvasive brain interface device that uses ultrasound to modulate brain activity, the technology represents the first start-up venture to pursue this unique approach with BCI technology.