Israel’s NYX has developed a headband that uses tACS (transcranial alternating current stimulation – a form of neuromodulation) to help insomniacs fall asleep. The headband checks your brain’s theta waves via its EEG connection and then trains your brain to increase them to 60% above normal.
https://www.israel21c.org/can-headbands-and-thimbles-cure-insomnia/