Well, they've done it. Japanese company Neurowear recently debuted their new robotic cat ear headband, dubbed "necomimi", at the Smile Bazar convention in Shibuya, Tokyo, which started April 28. The company claims the headband can "sense brainwaves" from the wearer and react accordingly by either twitching, folding down, or perking up. Neurowear has released a video of the ears in action (seen below) and have released a commercial for the ears, but have neither announced a date when the headband will become available, nor announced how much they will cost.
Still, there's nothing really surprising about their invention besides just how long it took.