It depends on what you mean by “work” and what your expectations are. There are slippers promoted as heated slippers that contain special insulation that are supposed to retain heat but do not provide any extra warmth. They typically don’t keep your feet warmer than just wearing a pair of wool socks. http://www.hammacher.com/Product/79784?promo=search
Then there are heated slippers with gel packs that can be heated up in the microwave that will provide a lot of warmth initially but the heat dissipates over a short time. http://www.cosysoles.ca/
There are also electric slippers powered by the USB port on your computer. The USB port on the computer is limited to how much power it can provide and therefore do not provide much heat. Plus you are tethered to a computer making it difficult to move around. http://www.usbgeek.com/prod_detail.php?prod_id=0502
Lastly, there are battery powered heated slippers. The best are powered by lithium battery packs that can recharged and used over and over again. They provide consistent heat at high temperatures giving your feet warmth for hours on a single charge. However, these are the most expensive and the price can exceed $100 for a quality pair. http://3volt.net/
So these are some of the options and as I stated earlier, it depends on your expectations and your needs.