I see it as an academic exercise, and not so much for practical reasons. The example of a glow stick I suppose technically qualifies as light, but does very little to illuminate surroundings to actually see something else. I might suggest a candle instead. They don't illuminate much, but still more than the glow stick.
Also the mre heaters utilize an exothermic reaction to generate heat. The materials used are magnesium and iron, both of which are metals.