Y'see, for Christmas, my sister gave me a package of
And they were the nicest. Things. Ever.
These things, when removed from their packaging, undergo a chemical reaction that causes them to produce approximately 100 degrees Fahrenheit of heat for about 5-6 hours. You use the adhesive on each one to apply it to the outside of your sock, on top and on the bottom of your foot. These things ensure that your feet feel warm for over 5 hours.
As a former Boy Scout, who has completed over 250 nights of camping, approximately a fifth of which happened during Ohio Winters, in tents (or sometimes with NO tents), I can safely tell you this: You can be wearing 5 layers of Thinsulate filled wool clothing on the rest of your body, but if your feet are cold, you will feel cold, no matter what temperature the rest of your body is at. There is NOTHING that feels worse than having cold feet. I speak this to you from bitter experience.
So I have to say that a product that can warm your feet up with no more effort than removing it from its packaging and applying it to your socks before putting them into your shoes HAS to rank among the top 100 of the Greatest Inventions of the World.