I'm so glad someone finally thought of this.
This headset combines three layers of all-weather protection with a high-quality pair of mini-speakers, allowing you to enjoy your iPod or any other portable audio device without exposing your ears to the cold. Layers of lightweight polyester fleece, Thermolite, and Polartec insulate the soft nylon-wrapped ear warmers (which can be stretched and adjusted to fit most heads), keeping your ears and neck warm even in sub-freezing temperatures. The ear warmers can be used by themselves when the detachable 5' audio cord is removed, and the around-the-neck design avoids ruffling your hair. The built-in speakers developed by JVC deliver crisp audio with an internal neodymium magnet and 40 mm driver. For convenient in-pocket or purse storage, the y can be folded flat upon themselves, taking up very little room while not in use. Spot clean. 3" W x 5" Diam. (1/4 lb.)
Click this link to purchase the Ear Muff Headphones from Hammacher Schlemmer.