fNIRS

https://www.synchronmed.com/

https://www.economist.com/news/technology-quarterly/21733197-can-brain-activity-be-deciphered-without-opening-up-skull-reading-brain

https://ctrl-labs.com/people/

https://www.openwater.cc/

Neural dust

Stentrode

https://www.neuroroboticsmagazine.com/nanotubes-go-with-the-flow-to-penetrate-brain-tissue/

They are related, and may form the foundational technology of, Brain-to-brain communication

Brain to Machine Interface: Future A to Z

Facebook builds brain-computer interface for typing-from-thoughts and skin-hearing! Crazy!

Neurable