I guess we often think of an improvement in the way most people live in a similar way to prof. Rosler, I posted this thread after seeing some examples of simple things that could change peoples lives for the better. Sadly, these simple things may make not people rich, so they do not get promoted.
So with the possibility that someone/something may help, here's some simple things:
First simple cooling. btw, something like this was used in Australia. I was born somewhere around a crossover point, where now common household goods started to become available and affordable.
In 1944, my father made an icebox. Built out of solid timber -with an inner and outer case and sawdust insulation. Cooling was by a block of ice, frozen at the local meatworks, (they had an ammonia plant and could freeze lots of ice). It extended the safe period for keeping meat and milk etc.
An even simpler method could be seen in some homes. Just a gauze covered cupboard, over which you hung wet bags, evaporative cooling did the rest. Not highly effective but better than nothing.
A similar concept is at work in this device, used for hundreds of years:
http://www.youtube.com/watch?v=ZNLPeb3qIhc