Sterno is about as safe as you can get but it will still deplete oxygen and does produce carbon dioxide (not carbon monoxide), so you still have to take some care in it's use. Aside from the obvious (cell phone, 2W radio, etc) I would add something to signal with. I have a large glass mirror, a flashlight, and a bright orange plastic sheet. A shovel is a necessity, and if you have access to wood a saw and an axe would be invaluable. Something to boil water and melt snow in would likely be necessary.

I keep two footlockers full of supplies and gear in the cap-covered bed of my truck. I figure I could hold out at least a week if I had to.

Regards, Vince

Edited to add: the orange plastic sheet is especially handy if you drive a white vehicle <img src="/images/graemlins/grin.gif" alt="" />