Most people think of medical supplies in an emergency, but survival supplies are just as important. Let's face it, you could drive off a road in the snow in a remote area in the winter and be stranded for days without injury, but perish due to a lack of preperation. This is especially true when we are offroad in a remote location or driving in lousy conditions.
A friend of mine knew a guy who died sitting inside his car waiting for help during a blizzard; he didn't take a warm enough jacket with him and he froze to death, the highway he was on got closed after he drove off the road - he wasn't found until days later.
There is really no excuse for a lack of preparation when you drive something as big a cruiser! There is a ton of storage space for emergancy goodies.
There are two books that are worth reading for those who are truely interested on survival, the first is the "SAS Survival Handbook" by John Wiseman and the other is called "Staying Found" (sorry I can't remember the author). John Wiseman instructs the British SAS survival school and his book covers survival in all regions of the world and for any situation. "Staying Found" is all about compass use and topo map navigation, something that all people who venture out into the woods should know how to do, especially when your PDA battery dies and the GPS quits working!
Buy a good knife that you can cut small branches with and skin annimals with if you have to, multi-knife may be handy but might not be up to these kinds of tasks.
Carry rope and learn how to tie knots! Very handy if you have to make a shelter, hike out of somewhere, belay or make a stretcher to carry out the injured.
Parangs are handy for cutting down bush; for building shelters or clearing a path through thick undergrowth.
If I drive in the winter I throw extra clothes in the car/truck and if its a long drive through a remote area, a down sleeping bag. Case in point, the frozen guy I talk about at the top of this rant! A warm down jacket and hiking boots that are water proofed, and for when its wet I carry a set of rain gear folded up.
Here's a few items out of Wiseman's book, some of these things he suggests you carry all the time:
-Matches: waterproof are best, but regular matches can be waterproofed by dipping the heads in wax
-Candle: provides light of course, but you can keep the interior of your car warm enough to survive with it and if you buy a tallow candle instead of a regular wax candle, you can eat it!
-Flint and saw striker
-Magnifying glass: to start fires with in the sun and to examine the detail in topo maps in case you have to go on the move
-Needles and thread
-Fish hooks and line
-Compass
-Topo maps: that show the area that you are 'wheeling/hiking in, in case you have to walk out and need to navigate
-Snare wire
-Flexible saw: (in a truck you could carry a bow saw) helps you cut firewood
-Medical kit that at a minimum contains the following:
Analgesic pain reliever
Intestinal sedative (Gravol etc.)
Antibiotics
Antihistamine for allergies
Water sterilising tablets for when you can't boil water
Surgical blades
Butterfly sutures (for closing wounds)
Band-aids
Condom - don't laugh

they can carry up to a litre (quart) of water
-Waterproof pouch that contains the following:
Dry packaged fuel for when you can't start a fire
Signal flares
Mess tin for cooking
Small flashlight
Mirror for signaling in sunlight
Brew kit - instant tea or coffee, powdered milk and sugar
Food - chocolate, dehydrated foods, electrolite powder etc.
Survival bag - heat insulating bag or blanket
Things I carry in my truck for my truck's survival, it beats walking if you can fix it!
Come-a-long
Fluids - Oil etc.
Critical belts - not a bad idea when you're really out there
Tow stap
Tubes of Liquid Metal (Epoxy) - poke a hole in the oil pan on a rock? fill the hole with this and fill'er up with oil
Emergency hose repair kit - plastic connectors with barbed ends, blow a hole in a hose? cut it in two and re-attach with one of these.
Small cheapo 12v cigarette lighter compressor
Plug kit for tires - poke a hole in your 2nd tire and already used your spare? Plug it and re-inflate it with the above cheapo compressor
A damn good flashlight so you can see what you're doing when you have to do all of this in the dark!
Small set of tools - important, that's why Toyota put them in every Cruiser they sold!
Odds and ends - hose clamps, teflon tape, rubber cement etc...
I can't think of anything else right now.