In a pinch, duct tape can temporarily repair a blown hose. If you have an exotic foreign car and you're going on a long trip, you should consider carrying extra oil, fan belts and hoses. An auto association membership. It's also a good idea to carry a bag of sand although you can always use your floor mats under the edge of the tires to give them traction. Have one for each traveler.
Pillows are a nice bonus.
Imagine you're going to be stuck in a snowstorm for several hours and pack accordingly. Finally, make sure your vehicle is regularly serviced. Take your car in for a tune-up whenever it's due and before any long road trip.