Nintendo can't detect your modchip, but I have always said that they can detect what you do, online or not.
I do mods, I done one tonight with someone that has just updated their wii to 3.0e.
I put in the wiikey config disc and it detected on the initial screen, but as soon as you click the game it will come up with an error saying
'an error has occurred. press the eject button etc'
I first thought that my config disc was playing up after using it for months. So I burnt a fresh copy....same thing!
My guess is that Nintendo can't detect anything hardware related, but they can detect what the name of the disc is that you put in. The gamecube homebrew of the wiikey config disc would have the same name worldwide.... They have probably realized the popularity of the wiikey and included code in their firmware to detect these discs.
This console has probably now been 'red flagged' and the next time there is an update, it will probably be banned from online services.
If you run the update disc on 2.2e, its fine. Its only the 3.0e firmware that can detect the disc.
I also thought that the firmware could detect if you are playing an international game (i.e. another feature of a modchip) - but then i realized that the wiikey will trick the console into thinking that the disc is PAL anyways.
This is all new, confirmed now on 3 consoles here including mine now.
So if you have updated:
- Don't stick in the wiikey config, or any game from a different region