Samuel K. Sia started working on how to miniaturize tools for diagnostic tests 10 years ago. When smartphones hit the scene, Sia—a biomedical engineering professor at Columbia University—decided to incorporate them into his research. He and a team of scientists have developed a new device that plugs directly into a smartphone and can simultaneously test for HIV and syphilis with just the prick of the finger. The results of their research were published in Science Translational Medicine this week. Sia discusses how this type of technology can make medical care more accessible in developing countries and what it might mean for consumer-driven healthcare in the United States.