I should, probably, decipher my EMDI - "electromagnetic devices improvisation" concept a bit more for clarity. That's a simple applied physics knowledge implementation for a survival situation with very simple tools and materials. Essentially, all you need is a long enough conductor, a powerful magnet, and an electric power source. Also the "right" flashlight, besides the battery (the power source), provides an electrical switch and a "visual indicator" (lamp of sorts) as well. You will be amazed of how many survival essentials you could improvise or enhance with that stuff, complementing a typical personal survival kit (aluminum foil is very important in it). From an electric conductivity, voltage, or current detector (to check and fix other electrical things) - to simple automation (like a security fence), or even a radio... In addition to that, I'm also carrying in my BOB and GHB several tiny 0.5Amp solid state DC voltage regulators (for different voltages conversion), tiny AC-DC rectifier (4 diodes in one casing), 4 solar film sheets the size of two playing cards stacked on the long side each (as light detectors and power generators), and a hunk of thin nichrome wire - for even more advanced EMDI projects.