Toss a Heatsheets Emergency Bivvy in the glove compartment, and you won't have to worry about your chances for survival should you have to spend a night in the cold. The updated, one-person version of the venerable Space Blanket, made by Adventure Medical Kits, weighs just 3.5 ounces and is significantly quieter than its predecessor. Designed to reflect back up to 90 percent of radiated body heat, the $15 bivvy is made of a newly developed polyethylene material and can be used as a temporary shelter as well as a blanket. It comes with its own stuff sack.