As far as ghetto mods go, this one certainly takes the cake. So if you loaded up Wii Fanboy today with the intention of procuring a slice of cake, you're out of luck.
Acidmods forumer Gene0514 escaped the plastic tyranny of cheaply-made remote attachments from dubious Chinese manufacturers by creating his own Wii-Sports-Tennis-compatible racket. There's nothing hi-tech about its construction; he basically just "secured" a controller onto a badminton racket with rubber bands. Even with the wrist strap fastened onto the handle, we can't imagine Nintendo ever condoning anything as precariously-fashioned as this for its games.
Swing past the post break for more photos of the setup and its v2 model, a remote belted onto an actual tennis racket.