I'm not going to pretend this is a professional opinion, but I did take a course on (believe it or not) Software Reliability last year. <br><br>Basically, there are two ways in which software (or anything else) can be made more reliable - quality, or redundancy. <br><br>Quality means, basically, making something to Mil Specs, or higher. The disadvantage to relying on this is that even the most expensive, well-engineered lighter can be lost.<br><br>Redundancy means having more than one. The disadvantage is that, if they're all designed the same, they can all fail at the same time. E.g. I found out last winter that my Coleman camp stove will not light at temperatures of -30. Having a second, identical stove would have been of no use. (It's important to read the fine print on your survival gear :-) Fortunately, my "backup" was a heated lodge with a wood stove. :-)<br><br>One technique used in Software Reliability is to have the same program written from scratch, to the same specs, by two or more completely different teams of programmers; this greatly reduces the risk that a single error condition will cause all the programs to fail. The point is, redundancy alone is not enough - you need diversity as well. I would carry a number of different tools - a couple of disposable lighters, securely bagged in plastic; maybe a mini-Butane cutting torch (can be used to make repairs); a couple of flints crazy-glued to the outside of my PSK; a Fresnel magnifier in my wallet. Maybe a Fire Piston, or a hunk of steel wool and a flashlight; some magnesium shavings wrapped in tinfoil and taped inside my SAS Gem Survival manual. <br><br>(A co-worker of mine, who is a professional in the area of Human Factors, lent me a book called "Set Phasers on Stun", by Steven Carey. It's a series of case studies of things that went wrong - usually with tragic consequences - due to some small, seemingly insignificant design flaw. While it doesn't deal with Survival in the way we tend to think about it, it is a well-written and interesting book, and a sobering reminder of how important it is to pay attention to the little things. ISBN: 0963617885 for anyone who's interested.<br><br>