Modified code from WiiWeight and uinput-joystick-demo
Creates a uinput controller with the inputs of the Wii Balance Board. No other drivers needed. Also runs on Raspberry Pi.
Connect the Wii Balance Board via Bluetooth. If the blue light stays on the Board is connected. Use ls /dev/input or tab compleation later to find out which one the board is. It should be the /dev/input/event* with the highest number e.g. /dev/input/event23.
Compile e.g. tcc wbb-uinput.c -o wbb-uinput. Run it with the path specified in stdin e.g. ./wbb-uinput /dev/input/event23. It works correctly if the values of the x and y axis get output to the terminal. Use AntiMicroX or other programs to configure the inputs to be seen as joystick, mouse or keyboard inputs.
See https://wiki.archlinux.org/title/Wiimote#Unable_to_open_uinput