Cell phones are being used as medical instruments in underdeveloped nations, extending highly cost-effective health care to underserved villages and rural areas. A team led by Daniel Fletcher, a Bioengineering Professor at the University of California at Berkeley has developed inexpensive conversions of cell phones into medical instruments, using clip-on lenses that cost one dollar or less. Fletcher's team has on-the-ground tests in Cameroon screening for parasitic worm infections and in Thailand screening for retinal diseases. "By attaching a simple set of lenses to a Nokia phone borrowed from my sister," wrote Fletcher, "we were able to image blood cells,……