The ground can get mighty cold in the wintertime, and your feet are going to freeze if you spend enough time outdoors. Think about it: if you stand on ice cubes long enough, your feet are going to turn into ice pops, too. That's why ThermaCELL has these Heated Insoles that come in up to men's size 13 (and down to women's 4.5) to go inside boots and shoes for work or play. The insoles are fitted with lithium batteries and microcontrollers that pick up a signal from a wireless remote that you carry in your pocket.
When you're in your 4x4 for hours at a time on the trail in cold climates, these Heated Insoles will keep your toes toasty.