A brain wave-activated tail wags when its wearer is happy. (Image credit: Neurowear/YouTube)

Soon you'll be able to smile with your tail. A Japanese company has developed a wearable tail that wags when you're happy.

It's called Shippo - Japanese for "tail." And it reads brain waves and heart rhythms to gauge its user's emotional state.

"A Shippo tail moves with your mood," the gadget maker Neurowear says in a YouTube demo.

The tail gets its orders wirelessly from a brain wave-reading headset and clip-on heart monitor. If you're relaxed, it moves softly and slowly. If you're concentrating, its movements will quicken, according to its maker.

Shippo also lets you tag your wag location and share your mood with friends over social media.

Unveiled Saturday at the Tokyo Games Show, Shippo joins brain-activated cat ears on Neurowear's roster of trendy technology. The ears, called Nacomimi, sell for about $160. The price of Shippo, which is still a prototype, has not been released.