“Nekomimi” = “cat ears.”
“Necomimi” is the brand name

via Robert who plans to sell them.

This perky reviewer demonstrates that they may not always work as well as one might wish.

I’m sorry to be a downer about this but having watched the demonstration I’m pretty sure that this thing is not reading brain waves. It looks like just another gadget that uses galvanic skin response to sort of simulate reading your emotions. That probably doesn’t matter to the fans.