Wind Up Radio and Torches
This has got to be one of the most obvious and brilliant inventions of recent times.
Simply wind them up and away you go. The radio has been a big hit in third world countries giving the ordinary people access to information when before a power source would be required. For the average folk in the UK, take one on a picnic.
As for the Wind Up Torches ... perfect. You only ever need them rarely [unless your an explorer or torch tester] and the batteries are always flat. A great place to put one is in the glove compartment of your car, for those times when you break-down along a country lane [speaking from experience].
Fit for purpose
Value for money