My car kit is based on breaking down at midnight in the middle of nowhere and having to walk back to civilization. You guys have hit most of the important ones. +1 on the poncho, which can keep you warm as well as dry and also make a tent and all that (likewise trash bags). Good idea on the day pack, then you can throw it on and be on your way. Matches & lighter both, they don't take much space.
Other ideas:
And an important addition - if you're getting the gear to keep in your wife's car, throw in an old pair of her sneakers or boots, in case she gets stranded while wearing heels.
Other ideas:
- Flashlights and batteries, chem lights
- Flares so other cars see you (also useful for starting fire with really wet wood!)
- String, cord
- Road map of state or US
- gravel or kitty litter if you drive on ice
- lots of water, but don't fill the bottles, so they have room to expand when the water freezes or gets hot
- mini first aid kit (with advil, neosporin, immodium (that can save your day!), band aids, mini bottle of that hand sanitizer stuff
- duct tape, gotta have duct tape
- ditto swiss army knife / leatherman
- big towel (can act as blanket)
- hat & gloves
- paper & pencil
- kleenex or a couple paper towels
- depending where you live and where you might be walking: sunscreen and bug juice!
And an important addition - if you're getting the gear to keep in your wife's car, throw in an old pair of her sneakers or boots, in case she gets stranded while wearing heels.