It's supposed to be a system where people can set up matches for games compatible with Nintendo Wi-Fi Connection, like Super Smash Bros Brawl or Mario Kart DS. The problems are that the game list has not been updated in ages, the widget was broken for well over a year, and no one truly bothers to use it. This is to be expected from a very old feature based on an online service that is already becoming outdated.
I didn't even know the NiWiFi setup was still there.
With no offense to Hull, its essentially useless. The game list hasn't been updated in a year, it's pretty broken and it's easier to just swap friend codes. I think it could be reworked, but for now it's just there.