Using Linux with Bluez
This site describes how to find your wiimote's bluetooth (MAC) address using Linux with bluez bluetooth stack.
It is very easy. If you are on a distro that uses Bluez3, just put the wiimote in discovery mode and use hidd in a terminal:
$ hidd --search Searching ... Connecting to device 00:1F:00:00:00:00 HID create error 13 (Permission denied) $
The connection will probably fail but you will get the MAC address.
You might have to get bluez and bluez-utils packages for this to work.
If you are on a distro that uses Bluez4, this might not work. In that case use your graphical user interface to find the wiimote and see its address.