This is pretty much the ultimate CAN bus hacking tool and will be the key to completely reverse engineering everything on the Leaf and other cars. Here's a video:
I made two devices, a quad CAN bus logger/bridge and a dual CAN bus logger/bridge. Both can accept and send data from either port and either pass it on undisturbed or modify messages on the fly IN REAL TIME. There's a serial port at 921600 baud that spits out all CAN messages including the message direction (in case of the bridge) or the port (in case of the quad CAN device).
If you watched the video, you can see that there are some bodge wires on the boards and a couple of issues with the firmware that I still have to resolve. So I will have to do a board revision. I know that a couple of people have asked in DMs and otherwise whether I'm going to provide this hardware for sale and... yes I am. I don't have a final price yet, but it'll be in the $40-50 range + shipping, sold on my Tindie store (http://tindie.com/stores/mux
Before I do that though, I want to put out the question: what features would you like on this board?
Both hardware and software. The hardware is all automotive grade, can withstand standard load dump voltages, conforms to CAN2.0B, the board is conformally coated and as soon as I have made an inventory of useful features I will publish a full datasheet. The boards will be firmware-upgradeable without any special tools (over an as of yet to be implemented USB mass storage bootloader).