Regarding the gadgets... If you are an Inuit hunter surviving off your skills successive implementation in the field daily (read 24/7) - you don't need any really. But if the great outdoors is just a mere 5%-10% of your life's time spending annually, it's better to have some to compensate for that severe lack of the practical experience. Multiply that by the diversity of the wilderness environments on the planet factor. There is no such a survival course or a book, which could be substituted for that deficiency, but there are plenty of daily survival tools polished by ages of wandering in the wild.