“Imagine you’re out in the middle of nowhere and you want to be able to diagnose malaria,” says Daniel Fletcher, holding up what looks like a cellphone sprouting a kaleidoscope. All you have to do is aim the phone at a patient’s wan-looking skin or a drop of blood squeezed onto a microscope slide, he explains. Then you point, click, and hit “send.” The digital image zips to an off-site lab, where a technician scans it for signs of disease and e-mails back an initial diagnosis—all in less than 10 minutes. “In developing countries, patients wouldn’t have to go to a clinic,” he says. “You could make a diagnosis right in the field.” Although many impoverished patients lack access to clinics, 80 percent of the world’s population lives near a cellphone tower.