A altoid tin is so insufficient to carry even the basic needs, I don't see a point in them, except that some folks will carry them because they are never going to carry a full sized kit. I have always found them intriguing, to see if there is a viable option out there. So far, have yet to find one that can replace my kit. It takes a full fanny pack to carry mine.
I have to respectfully disagree in that an Altoids kit shouldn't replace a BOB or dayhike kit. Rather it IMHO should be used for a small possibilities pouch or last ditch item when the irresistible force known a entropy has gotten the upper hand aka kit was washed down river, burned, stolen etc etc etc. Before I go on an Altoids thread with out photos isn't all that fun....
Ok now with that out of the way lets review how it could help.
A. Fire. Yes I have the skills to do friction fire. I can use my carbon steel knife and a few types of natural tinder to get a coal but is this something that can be depended on? Not IMHO however even my standard Altoids tin has multiple ways to start a fire.
1. 6 large strike anywhere matches in small plastic bag.
2. 1 backpacker szied mag/ferro block, USA made. Tinder and firesteel in one package.
3. Hacksaw blade.
4. Charcoth in small plastic bag.
5. Compressed cotton tinder.
That is 3 ways to start a fire plus 2 sources of tinder, not including the BandAid and anti bacterial cream packet both flammable. Yes I am getting a fire going and that's a good thing.
B. Cutting.
1. There is a small SAK. Will it take down a tree? No but I used the tweezers to remove a splinter during a camping trip. Also the blade is sharp.
C. Cordage.
1. About 12+ feet of fishing line wrapped around a larger plastic bag.
2. About 12+ feet of nylon cordage whipped on the outside. I went with it over paracord because that made the kit too thick for the leather pouch to comfortable remove.
3. 3+ feet of sewing thread.
D. Signaling.
1. I have an English metal whistle that will blow your ear drums out. Used it on a hike with my nephew and his two friends 6-7 years old to call them back every time they tried to wander too far from the group. Also if I had to yell for help it would sure be louder and last longer than my voice.
2. I have some Al foil folded up. Maybe it would be more reflective than the palm of my hand or maybe not?
E. Food.
Ok this is silly but what the heck.
1. Fishing line and 2 flies and hooks.
2. Wire.
The green wooly bugger (never know exactly how to spell that...woolie, wooly or wooly) will catch nearly anything from pan fish to trout. I hard to replace one that was given away to a friend during a fishing trip. He was burning through my files like they were candy. Like I said an Altiods kit can be a working kit. Wire snare? Probably not. LOL!
F. Light.
I have a small PT amber LED keychain light.
G. Repair.
I have a sewing needle with thread. I must have replaced the thread multiple times sewing buttons back on. The fatter I get the more wardrobe malfunctions seem to befall me.
H. Water. About a year ago I had two water tabs but used them during a camping trip. Those need to be replaced. Also there is a plastic bag which might or might not hold water as it has been folded so tight for some time. That said I am about to say something which I hope is taken within the proper context. I don't know every water born illness however most in my neck of the woods and guessing other places as well takes 5-7 days before it hits. I had giardia and it is no joke but I wouldn't last 3 days without water. If I am not found by 7 days somehow I think the search would be for a body. Basically if there are no other options and by definition surviving with an Altoids kit (is there any documented cases) is a last ditch thing I would simply drink the water. Maybe I would attempt to boil it first in the tin etc etc but I am drinking no matter what if there is water.
I. First Aid.
BandAid and anti bacterial cream packet. I have replaced these several times.
I could go on but by now guessing it should be clear that an Altoids or other very small kit isn't perfect unless it is all yea have or if it is handy. The same basic answer applies to those "what is the perfect knife" threads. The knife or kit someone actually has on their person is perfect because that's what yea got.