What's this?

Nathan just bought the weirdest thing the other day... its a tennis racket for swatting flies & mosquitoes ... wasn't quite sure what it did or how it did it, so I was messing around with it and realised you had to turn it on??? What the... oh it has a light ... as I then bounced the strings off my knee ... and proceeded to electrocute my leg, in a huge shower of blue sparks and a yelp of pain as it turned my leg numb for half an hour! and then I had pins and needles for an hour after that!  Lesson learned, don't mess around with Chinese technology!