Yes, the idme utility is the key. Getting access to it through Jailbreak and Usbnet is the process. Once you type idme -h everything becomes obvious. However, I thought it had failed because the serial number didn't actually change until I'd rebooted, so was kind of surprised to see it in settings.

BTW, there's no mac address to change on the K2i. And I think the board id can only have two values.