If you have your Wii in a small room, this probably isn't for you as it's very easy to get carried away swinging it around like a sword.
Also, if there's people in the room watching you, make them sit down against the wall behind you. They're least likely to get hit there.
Not a necessity by any means, but it does make the odd game slightly more 'realistic', and can be highly entertaining.
If you can get one cheapish and like your realism, go for it! But otherwise... buy another game or some chocolates. =)