Most open source modchips cost like $3 and does the exact same as the $40 WiiKey. It requires 5 wires to solder and there's no way for Nintendo to 'patch' it since it's only hacking the DVD drive and the DVD drive is not upgradeable. There are new Wii's that has newer chip or solder points removed but it only start to show up recently.
The Wii has no warranty sticker on it and thus noway of Nintendo to prove it's been open. And I have heard of people successfully getting their replaced by Nintendo even there are very obvious signs of failed modchip attempt.
I'm not encouraging modchips, just stating some facts.