... they will probably help you avoid amputations due to frostbite.
That made me laugh out loud. Perhaps inappropriately, but it did.
I would include a flameless cooker or MRE heaters. Might as well have a bit of luxury. For that matter, put some really nice items in your food stash - really, really nice chocolate bars, for instance.
I like the way you think, Hikermor.
Because my dog and I love bikejoring, winter is my favorite season here. Have gotten in the habit of packing two or three thermoses of boiling hot water along with cocoa packets so fellow bikejorers (and dogscooterers) can warm up from the inside on the trail.
When faced with a long winter drive it would be a good habit to have those thermoses, boiling water and cocoa (tea or coffee) along. Even after sitting overnight (in my kitchen) my smaller LL Bean thermoses are keeping water hot. Quite hot.
To augment my thermos inventory for group outings, this one is being delivered today:
http://www.amazon.com/gp/product/B000U8D...d=ATVPDKIKX0DER.