The wii itself is not needed. You can simply go buy a replacement wiimote and use that.
You only need to power up the wii to power up the led bar that comes with the wii, Assuming you have a wii and are using it for the demo. However if you go buy a wiimote by itself you will need to make a "led bar" or some variant of that and power the leds. The led bar that comes with the Wii is just 2 IR leds, nothing more. Hope that helpsJohn