Want to develop a game for the Wii, why not use flash and put it on a website. Have a look at www.wiicade.com - remote works great with these flash games?
Want wireless streaming for mp3s and video? - well this is my next investigation because the wii takes ip addresses thus having your intranet!
So in theory you all need now is a flash media player(which can handle MP3s and Video) and shove it on a local web server. Point the player at the local files etc.
I'm going to look into this and post back. But I already have a intranet running with my C# .net applications, so I'm excited with this potential (being a programming)