It's common for animals to wag their tails uncontrollably when they get excited, so wouldn't it be great if humans could, too? Oh, wait, we don't have tails. Enter the Tailly: a robotic tail extension created by Shota Ishiwatari (the same guy who helped develop the Necomimi cat ears).
The Tailly knows when a person is excited by measuring their heart rate using sensors padded along the inside of its belt. Tailly wags when a person's heart rate increases and sags when their heart rate drops.
Ishiwatari says on the Tailly's Indiegogo page that customers who liked the Necomimi wanted a matching robo-tail. Thus, the Tailly was conceived.
As strange (and wonderful) as the Tailly is, it hasn't been able to get the necessary crowdfunding required to turn it into a commercial product. The Tailly project failed to reach its $100,000 goal on Kickstarter and the Indiegogo campaign looks to be headed in a similar direction. As of this writing, there is 34 hours left and the project only has $15,870 of the $50,000.
Ishiwatari, if you're reading this, maybe pair the Necomimi cat ears and the Tailly together? They make a natural set.