My girlfriend is staying about an hour away at her university several days a week, so I added some things to her car kit in case she is stuck there. In addition to a basic survival kit (ponchos, poncho liner, bivy sack, some lifeboat rations, several 1 liter bottles of water, metal water bottle, water filter, knife, several methods of fire starting, cordage, headlamp with extra batteries, IFAK, boo-boo kit) and a 20 degree rated sleeping bag I added an isobutane camping stove with a fuel canister and a three-day supply of freeze-dried food. This way if she is caught by a noreaster or hurricane etc. she can at least have a few days of food ready to go. I also bought a wind-up/solar powered emergency radio with phone charger function. She also has a car jumper pack that can be used as a phone charger. I know she at least won't freeze (sleeping bag + poncho liner + jacket I think she would be OK) or starve. We are going to go over how to use everything this weekend.
I also keep an E-tool, windshield scraper and basic tool kit in each car.