Smart phones can pay our bills, track our diets, and record our slumber. Soon they may become a leading weapon in the global fight against disease. Researchers have designed a cheap, easy-to-use smart phone attachment (shown above) that can test patients for multiple deadly infectious diseases in 15 minutes. All it takes is a drop of blood from a finger prick. Pressing the device’s big black button creates a vacuum that sucks the blood into a maze of tiny channels within its disposable credit card–sized cartridge. There, several detection zones snag any antibodies in the blood that reveal the presence of a particular disease. It only takes a tiny bit of power from the smart phone to detect and display the results: A fourth-generation iPod Touch could screen 41 patients on a single charge, the team says. The researchers conducted a field test of the device at three Rwandan community clinics, where health care workers rapidly screened 96 patients for HIV and active and latent forms of syphilis. Compared with gold standard laboratory tests, the dongle was 96% as accurate in detecting infections, missing just one case of latent syphilis, the team reports online today in Science Translational Medicine. Despite a 14% false alarm rate, the researchers say the device’s high sensitivity and ease of use make it a powerful tool for diagnosing these deadly diseases in the field, particularly among pregnant women. The researchers are now preparing a larger scale trial for the $34 device, which they hope will let mobile clinics and health workers provide rapid and reliable disease screening in the remotest areas of the world.