TMS/TDCS has been used in wearable neurostimulation devices for 20 years to treat a wide range of symptoms
These devices work by stimulating the brain to produce neurochemicals such as serotonin, while modulating the default mode network and entraining alpha waves. These devices have been used to treat insomnia, sleep issues and depression but is not a sedative - instead, the device modulates the brain to produce a restful state that accelerates sleep onset and restores longer periods of sleep.
PBS Broadcast here https://www.youtube.com/watch?v=yoEu2mEdLjw
News Broadcast https://www.youtube.com/watch?v=Iu0H0csxLmM