How about this for a cool USB gadget that warms up your slippers for you. Simply connect your slippers to your computer to warm them up.
Once the battery is full you disconnect the wires so you can walk around the house, then reconnect to reheat.
If you like the USB Slipper warmers gadget then you will be equally impressed by the USB hand warmers. Great gadgets for the winter months and if your boss at work is a scrooge and doesn't put the heating on!
Online gadget shops such as I want one of those and Everything USB sell these USB Gadgets to keep you warm in the winter.