My Wii Sensor Bar is built of two arrays of IR-LED that get its power from a proprietary port on the Wii / WiiU. Since I have a beamer as second screen with its own Sensor Bar, a Wii-to-HDMI-Adapter and a 4x2 HDMI switch I don't want to unplug and reconnect the sensor bar cable anymore when I switch from one screen to the other.
My idea: connect one sensor bar to the USB port of the TV, and the other one to the USB port of the beamer, so both will only be enabled when the specific screen is in use. Another reason to get power from an external power supply could be that you have both, a Wii and a WiiU.
So, I've tried to find out what current and amperage the sensor bar requires, and since I did not find any reliable information I've took a screwdriver, my multimeter and had a look at it.