I have a Memorex Motion+ remote which works fine with extensions, but using the power button on it will hard crash homebrew apps, requiring a Wii reboot.
One reports as a malfunctioning Classic Controller.
One doesn't detect at all.
One works but reports ranges higher than a standard nunchuk.
Another one will sometimes lock up the Wiimote when plugged in (requiring only the Wiimote to be powered off and back on), but other times it works as above.
The Wireless Memorex Nunchuck won't work with the Memorex Wiimote+, but it will sometimes work with an official Wiimote, usually only after I plug in and unplug an official Nunchuck first. So try that if you have problems with off-brand extension controllers.
And drums seem to report as a guitar that mostly works but has some errant input (no clue how to properly read drums; good documentation is nonexistent).