Manu Prakash on TED.com (Stanford professor)

at about 3 mins 30 he tells us about a medical centrifuge given to an African clinic where there was no electricity, used as a doorstop! So he set out to find a zero power centrifuge. His innovative journey took him via a yo-yo, a spinning top and he regressed to the oldest toy known (about 5000 years old) the spinning button which he demonstrated using paper and string. On his own blood, citing the ability to detect anemia with a little clay, capilliary tube & sellotape on the spinner. No electricity was hurt in the demo.

He shows an array of spinners all designed to assay specific ailments and even one to do about 8 on one spinner.

For me the wonders of technology (I use it to the full) are pretty passé in the face of such extraordinary simplicity.

Any other examples come to mind?