Every now and then a new product comes along that seems to obvious in retrospect that you’re surprised no-one had thought of it before. I wrote earlier about the nifty BioLite electricity-generating stove that couples the gasification principle with the thermoelectric effect (real space probe technology!)
The Estream is another great example. Estream is a portable hydroelectric generator that fits in your backpack. Simply dunk the mini-turbine into a fast flowing stream or river, and the device will convert the energy of the moving water into electricity to charge-up on the internal battery. This stored energy can then be used to charge any USB devices, or even power the integrated light as a hangable lamp.
Perfect for taking on camping trips, or making a big difference to off-grid living and providing for yourself if civilisation ever did collapse!