GC/Wii homebrew to send over multiboot .gba roms to a gba using the gc gba link cable.
All you need is a folder called "gba" on your main device (sd gecko on gamecube and sd/usb on wii) and put in some multiboot .gba files (256kb or smaller).
If you then start gba-link-cable-rom-sender you can just select the file you want and transfer it to your gba in port 2 by pressing A.