The SOL survival blanket reflects up to of your body's heat back to you and is sized to shelter 1 - 2 adults. Available at REI, Satisfaction Guaranteed.
DRIVING FROZONE: How to keep your water warm in freezing conditions, it's not as easy as you think. The 3-step program follows: Step 1: Don 't keep your water in the trunk, it'll freeze. Instead, keep it up front near the driver. Near the Heater. Warm water is better than frozen water. Step 2: Use a cheap styrofoam ice chest or plastic cooler for your drinks. This way your water won't actually freeze. Step 3: Wrap your water bottles in one of those Mylar survival blankets.