A different kind of Google map; also see How a Google Engineer’s Bike Crash Shows Potential of Nanoparticle Project (WSJ) and “We’re Hoping to Build the Tricorder” (Steven Levy on Medium)
"Google is designing a suite of nanoparticles which are intended to match markers for different conditions.BBC News - Google is developing cancer and heart attack detector
They could be tailored to stick to a cancerous cell or a fragment of cancerous DNA.
Or they could find evidence of fatty plaques about to break free from the lining of blood vessels. These can cause a heart attack or stroke if they stop the flow of blood.
Another set would constantly monitor chemicals in the blood."