The Nintendo Wii's pack-in game Wii Sports is a pretty decent proof of concept, but waving around the Wiimote isn't exactly a realistic experience. However, by attaching these plastic, erm, attachments, you can authentically recreate the experience of swinging a baseball bat, golf club or tennis racket. Take a look for yourself at all of them on the other side.
So, in essence, you're paying $22 for pieces of plastic shaped like sports apparatuses. I can think of bigger wastes of money.
Product Page [Videogame.brando.com.hk]