GeckoReader is a program to be run under Windows that will open a command prompt and output what it reads from a USB gecko. You must have the USB gecko installed, set up the COM drivers, and have .NET 2.0 for this to work properly. Then whatever buffer is sent from the Wii/Gamecube should pop up on the screen.
libgeck
Also included is libgeck. It is a very small lib that you can link your programs with that should aid in debugging. Just link this in the makefile with -lgeck and put the .a and .h files in their directories in your devkit folder. Since this is a wrapper for the libogc functions, you need to link that as well. Or you can just copy the .c and .h files to your project and #include them. The gecko must be in slot B.