Here's how to make some emergency crampons for walking on snow and ice. They are made out of easy to find chain and paracord and can be kept in a plastic sandwich bag. You can keep them at home, but a better place is probably in your car. The paracord uses an adjustable knot to fit over whatever pair of shoes you are wearing and won't cut into them like an all-chain crampon might. These things give you amazing traction even walking on ice. They could easily save you from a nasty fall.
The two essential supplies would be chain and paracord. These can be found at home improvement stores or discount stores. I used #3 chain which worked well. The size of the chain isn't the most important thing, just make sure you don't get so big of a chain that you can't cut through them with wire cutters. I used a lighter to melt the ends of the paracord so it didn't fray. The spit rings and carabiners aren't absolutely essential, but are nice to have. You can get split rings at craft stores. Consider getting a pair of split ring pliers to hold the rings open when you are working with them (that's the tool in the upper right hand corner next to the rings).
The two sets of crampons for each boot are mirror images of each other. The left boot is illustrated here. With either boot start the end of the chain at the front *inside* edge, across the bottom approximately where the ball of your foot would be. Bring the chain horizontally across to the other side of the toe, then turn and make a long diagonal "Z" to the inside of the heel, and then another turn to lay the chain across the heel. It's best to leave a little bit of extra chain that you can cut off at the end. I put a split ring at each of the four points on the "Z" to make it easier to tie on the paracord.
The crampons use two pieces of cord to secure the chain to the boot. The 'toe strap' is a short piece of cord over the top of the toe, connecting each of the split rings underneath, as the picture shows. Make an 'overhand loop' on the end of the cord to attach to the outside split ring first. Then run the cord over the toe and tie a 'Blake's hitch' knot to the other split ring on the inside edge of the boot. Until you finalize everything leave a long tail on this piece before you cut it. You can find plenty of great videos on the web for both the 'overhand loop' and 'Blake's hitch'. The Blake's hitch is an incredibly useful knot that can be adjusted looser or tighter. This is helpful because we want the crampons to fit whatever shoes you happen to be wearing. Planning for a worst case scenario you should probably make the fit for whichever shoes you are most likely to be driving in. If you get caught at work or outside in your car you won't be able to make adjustments like you could at home.
The second piece of cord begins with another overhand loop attached to the inside edge of the heel. Then bring it around the heel and make another overhand loop to attach to the split ring on the other side. You could also probably use a Blake's hitch here for the second loop to make the heel strap adjustable if you wanted.
Continue running the cord around the outside edge and then over the top of the boot to fasten it to the other side. Pass the cord through the toe strap to keep things snug. Then tie the end of the cord in another Blake's hitch and attach it to the split ring (or a carabiner as in the video) on the inside edge of the heel. Using a carabiner will make it much easier to take the crampons on and off.
The crampons take up hardly any space and can easily be saved in a sandwich bag and stored in your car, at home or at work. They are very inexpensive and making a couple extra sets is hardly more expensive than making one. Consider giving them as gifts! Make sure you label each one 'Right' or 'Left' with a piece of tape around the ankle strap. It will make it much more easy to put on in an emergency. You can probably think of other ways to make improvements - Reflectors? LED lights? Use your imagination! Watch the video for an overview of how to put them on.