The aptly-named LifeStraw is an invention that could become one of the greatest life-savers in history. It is a 25 cm long, 29 mm diameter, plastic pipe filter and purchased singly, costs around US2.00
...LifeStraw is a personal, low-cost water purification tool with a life time of 700 litres – approximately one year of water consumption for one person.
A lot of the gee-whiz about this technology concerns its potential in underdeveloped countries, where people lack clean water and suffer from a high rate of disease as a result.
But it strikes me that this sort of technology has potential to affect life in developed countries as well. If you could decentralize water purification, electricity generation, and security against violence, what might that do to social structure?