NSA Exploit of the Day: IRONCHEF

Today's item from the NSA's Tailored Access Operations (TAO) group implant catalog is IRONCHEF:

IRONCHEF (TS//SI//REL) IRONCHEF provides access persistence to target systems by exploiting the motherboard BIOS and utilizing System Management Mode (SMM) to communicate with a hardware implant that provides two-way RF communication.
(TS//SI//REL) This technique supports the HP Proliant 380DL G5 server, onto which a hardware implant has been installed that communicates over the I²C Interface (WAGONBED).
(TS//SI//REL) Through interdiction, IRONCHEF, a software CNE implant and the hardware implant are installed onto the system. If the software CNE implant is removed from the target machine, IRONCHEF is used to access the machine, determine the reason for removal of the software, and then reinstall the software from a listening post to the target system.
Status: Ready for Immediate Delivery
Unit Cost: $0

Page, with graphics, is here. General information about TAO
"CNE" stands for Computer Network Exfiltration. "Through interdiction" presumably means that the NSA has to physically intercept the computer while in transit to insert the hardware/software implant.
In the comments, feel free to discuss how the exploit works, how we might detect it, how it has probably been improved since the catalog entry in 2008, and so on.
The plan is to post one of these a day for the next couple of months.