I don't think so. Certainly not for any peripheral that is allowed to do DMA. Though plugging in a malicious firewire peripheral is a lot more practical than replacing the battery...
When there's already semi-legitimate worries that the Chinese government could have spyware chips installed on computer motherboards, this would be a lot more malicious, easier to perform and initially far less detectable.
From the post, the author says the battery could repeatedly install malware or spyware to your computer.
What would be more worrying is if someone found a way to hack directly to you battery. IE a virus you get installs itself to your battery as its resurrection method rather than in a system file. Worse yet would be if someone maliciously wrote a virus that caused your battery to overcharge a month down the road.
Imagine all those stupid MSN virus' if they could fry your laptop battery.
You don't need a government's resources. You need a programmable firewire device, like an embedded Linux device. You also need ten seconds of physical access to their FireWire port. That's a lot easier than hacking a battery and convincing the target to use the battery.
