Check out this BBG post: Manufacturer confirms chip: iPod headphones now have the Apple Tax; Update: Apple confirms no DRM, authentication, just licensing — turns out Apple didn´t use DRM on the headphone interface, just a proprietary chip you have to license if you want to claim ¨Made for iPod¨.
Fred von Lohmann from the Electronic Frontier Foundation sez, "The sharp reviewers at iLounge spotted out a misfeature in the new iPod Shuffle that other reviewers overlooked: third party headphones for it apparently will require an Apple 'authentication chip,' something that is already required for various iPod docks. Yet another example of Apple's DRM hypocrisy. Apparently it's OK for Apple to use DRM to lock in consumers and hobble competition, even as it rails against DRM on iTunes music."
Update 2: We took one apart and found a mysterious chip inside the new Shuffle's headphones. Have no idea if it's DRM or not — Rob.
Update: We did a quick test in the gadget dungeon: existing inline headphone control adapters for the iPhone and other iPods won't work in the new Shuffle. — Rob.