I recently lost my emergency kit.
This gave me the opportunity to rethink what exactly goes into my kit. You put stuff there, and if you're doing it right things will come out of it, but only on pretty rare occasions. As a result it's easy to forget what you actually keep there. On that note, here's what I have in my kit.
Waxed twine or flossThis is for general ad-hoc gear repair. Sometimes I'll bind something back together, most of the time I'm stitching clothing, a pack, boots, or something similar.
Steel wireAgain this is for gear repair. You can fix a lot of gear with steel wire, you'd be surprised. It can replace a cotter pin and things like that in very secure way more easily than with twine. Due to it being stiff you can re-thread a pulled out draw-string. Additionally, I once used it to attach the exhaust system of a car to the car so we could get home without it dropping off.
duct-tapeOf course! This is useful for just about everything. Duct-tape is one of my favorite blister treatments. It's great for gear repair, especially for a quick-patch to a backpack. I use this constantly. It really can't be stressed enough just how useful a bit of duct-tape is. I usually roll it on itself off of a full-sized roll. Though I've also baught the mini rolls and those work to.
Note - putting it on your nalgene drinking bottle really doesn't work well. That will get wet a LOT and the duct-tape won't come back off very well.
emergency bivyBy this I mean one of those reflective "space blanket" style ones. They're just like the blankets but sealed across an extra edge. This makes them far easier to use as a bivy, and if you want them open you can always cut that edge again, and voila! I have only used this a couple of times. The last time it's because I was trying sleeping with 2 blankets up in mendecino. That didn't work out so well, but I had my bivy! lining the bivy with the blankets I had a fine nights sleep - while my friend couldn't get to sleep and had to beg fire and more blankets off someone else. I consider this a potential/probable life-saving item.
Aluminum foilThis has a lot of uses. I admit to never having actually used it though. Some examples include a solar still, and a signaling mirror. In the past I depended on the aluminum foil I already had for my alcohol stove's windscreen. Now I'm often carrying a wood-stove instead (or in addition, but it acts as a windscreen), so I've added aluminum foil back to the kit.
medical kitI store this in a tiny nalgene bottle (like the ones people keep peppermint soap, or spices in). This keeps everything dry. I then store in that bottle
An oversize sharp needle with a large eye
: As a medical item this can be used for ad-hoc stitching if you have to (I don't really know how, but if it's what you gotta do, just do it). More useful is popping blisters and draining infections. Additionally, the large eye lets me use it for stitching up packs, boots, shorts, or whatever.
: An anti-inflammatory. This is one of the most important things to carry. If you get a muscle or tendon injury this will help keep it from swelling to the point of not flexing anymore. It will also help speed healing of a lot of muscle injuries. I also have some knee problems that are inflamation related - this actually helps them HEAL, besides letting me walk on it. If you need it and have a high drug-resistance you'll want a lot. I try and carry at least 2400mg, enough for 3 doses for me if I really need it.
: I don't carry this for myself at all. I just carry a little for others. For many people who gets migraines this is *the* solution. In particular it can be used to avoid the migraine entirely if applied while they only have visual auras. As an added bonus it's another anti-inflammatory at high enough doses - so it's useful if someone can't have ib-profen due to a weak stomach lining, (ib profen can cause ulcers). I've never had this when I needed it.
: For allergic reactions. Now, I'm not a doctor, so please don't take this as medical advice. That said, it's fairly common to give someone double or more the recommended dose if they are allergic to bees and get stung. This can often keep them from going into anaphalactic shock. It's also great for reducing reactions to poison ivy or other histamine reactions. It doesn't make me drowsy at all, if it does you may prefer another option.
: This is a must. If you are awesome at stitching you might not need it. Short of that this is in my experience one of the best pieces of emergency gear to keep you on the trail. Impact and slash wounds are some of the more common when backpacking. These create nasty splits in the skin. A butterfly suture is a special band-aid designed for closing these wounds. Often they can be used in place of stitches (such as on my mom when she needed 3 stitches after hitting her head on a rock).
Additionally I depend on having some bandanas around to use as a sling and duct-tape for closing wounds and as blister treatement. I often carry gauze, which when combined with the ducttape, can make a very large bandage if needed.
Albutoral InhalerI'm asthmatic. If I can breath I can deal with a heck of a lot more more problems. If you have a necessary perscription drug, it's really worth carrying an extra somewhere in your pack.
PencilYou can always use the corner of your map. Having a pencil is useful if you get seperated from your hiking buddies for example, you can leave them a note. Additionally you'll find you want them for filing out little passes and things when getting camping spots, self-registering at a trailhead or whatever.
Non emergency kit emergency gearNow, they always say that one way to drop weight is to make dual use of your gear. There's no reason that your non-emergency gear can't get included when thinking through what you'd do in an emergency. In particular here are some of the pieces of gear I depend on.
Miniature knifeThis is a bit silly, this is my backup knife. I mostly have it so I can attach it to the lanyard, and have the lanyard stay light - so I'm not discouraged from throwing it around my neck when I drop my pack. I tend to carry an excessive number of knives.
"Light-My-Fire" sparkerThis is basically a flint-and-steel, but it throws a better spark. Jess and I use these to light our alcohol stoves normally. I often carry an additional lighter, but I don't trust those. This is my "will just work" backup for general fire-starting. I've spent a while practicing starting a fire with one such that I can do it in non-ideal conditions (though still not as non-ideal as I'd like).
Photon 2These are great. Many people use them as their *only* light source, and I have actually night-hiked with one. It works fine on-trail if you're used to night hiking. I like to have a spare light-source though. Probably 4 separate times I've been out on a trip when someone realized they left their light at home, or their light broke. In my system being able to walk is one of the most important safety measures this includes at night. A backup light is not a high-cost and it may make a trip far more pleasent when someone else forgot theirs. I also carry an additional clip for it so I can clip it to my hat, or a bandana tied to my head and use it like a headlamp. I should note that this uses the same batteries as my normal headlamp - so it also acts as a backup for batteries.
WhistleI find that I often want it when running off to check a bit down the trail. You can set up a standardized whistle system in your group. 3 whistles is always emergency, so Jess and I set up 1 whistle as "SIN" and "ACK". Think marco-polo. This lets you query for the other person's location even at a distance. 2 whistles is "Come here", but not an emergency. This way you can signal when you've found the correct path.
Button CompassI used to always carry a map compass. It depends a lot now, I realized a map compass is rarely what I really want anyway. I either want a sighting compass, or a button compass is good enough. I carry a button compass in my emergency gear so I just always have one and don't have to worry about it. This also gives me a backup were I to lose my large compass - as it tends to come in and out of my pockets a lot.
LanyardYou may notice that this stuff isn't in the emergency kit.
Instead I keep the last 5 items on a lanyard in an easy to reach pocket. This way when I say... go off to fetch water a mile or 2 away, or run down a trail to see if it's the right direction, or whatever, I can just grab the lanyard and drop my backpack.
Survival KnifeThis is just a folding knife or a belt knife (I have both) with a good bland and a handle large enough to easily wield the blade for things like basic woodworking. Starting a fire without a knife is much much harder. This is also useful for cutting pine boughs for a shelter, and any wood construction.
Leatherman squirtThis is a *great* tool. I have the one with the pliers. There's nothing like sewing a boot to make you wish you had a thimble or pliers. Or fixing a stove you suddenly realize you need an awl. A small screwdriver to fix who knows what, a file to modify the zipper on your sleepingbag so it will mate with your partners (yes I did this, it *almost* worked). A full-size leatherman is just larger than I find I need, and very heavy. The squirt is perfect. I never use the blade, so it's nearly sterile and very very sharp - perfect for a quick minor surgery to remove a giant splinter.
Stay tuned: I'm rebuilding my emergency kit, so this may well get updated as I realize bits of gear I'm missing :).