Not offering an Ethernet connection to supplement the Wii's built-in WiFi has always been considered a strange decision, if you ask us. Nintendo clearly realises that not everyone (if you can believe it) has wireless because it is, in Japan at least, pushing out its own wireless bridge. After all, if your customers have to buy an adaptor to get their Wii connected to their wires-only router, why not make it yours?
As well as offering an Ethernet connection to a router, allowing the Wii to get online, the Ninteldo Wii WiFi Network Adaptor has a second port, allowing any wired device to plug into adaptor and get wireless. According to Nintendo's site, any device can be connected, but only the Wii, DS and DS Lite are supported officially.
The device supports WPA-PSK and 128/64-bit WEP encryption, for securing the wireless network. Given the last network adaptor Nintendo offered was a USB affair, that required a PC being left on to use it, this offering is a much better solution. At ¥5,800 (~£30) it's not too expensive, though, you'll have to be in Japan to get one for now.