As I mentioned in the gloves thread, I have 12V heated clothing which is great but you have to be plugged in, so it’s only usable on motorized vehicles. I’ve looked at some of the lithium battery powered alternatives with interest, but stories like these worry me. The old school D-cell heated socks placed the battery up on your calf above the boot in a pouch where it was easy to remove. If a D cell is short circuited, it becomes a fire and burn hazard but at least it’s not going to explode. Putting the lithium batteries in the boot seems riskier and this story seems to confirm that. Besides, I don’t think any of these products are designed for water immersion.