RiiConnect24 is a custom server replacing the WiiConnect24 server that ended on June 23, 2013. It was created by Larsenv, PokeAcer, and AwesomeMarioFan.
Relevance to Mario Kart Wii
With RiiConnect24 activated, you can play the "Ghost Race" mode and check rankings for Time Trials. As of now, you can't compete in Tournaments.