All you need is the component cable... but Wii doesn't support HD. You'll just be seeing it in standard-def, widescreen/480p. Which is still nice.
Wii doesn't support HDMI cables, so don't sweat it.
But for any future devices you get, HDMI is a good alternative to the 5 connections that component cables use. But don't ever pay $50 for them. Get them for $5 at monoprice.com.