I2C Wushu looks great. It's cool that it's all in an Arduino sketch.
Looks like you've copied the Bus Pirate syntax just like I did.
One of the nice things about my Bus Ninja is that it's got USB support (on the right AVR chips), meaning that there's no need for the external FTDI USB chip. Also, it can emulate other USB devices, eg. mass storage/HID.
There's also a mini cooperative multitasking OS under the hood, so it can run background tasks while handling user commands.