It's possible to track these currently, but the technology isn't very portable or cost-effective for day-to-day care. By creating a device that can do the same job, but weighs just a tenth of a pound, cancer suffers could keep one strapped to their bicep for real-time tracking of their medication. It works by firing an angled laser at the skin, with the microscope then capturing the illuminated image that's produced afterward.
This data is then sent back to a computer where an algorithm filters out the noise generated by the skin itself. The resulting image can then let doctors track the chemicals in isolation, and if the tech can be developed further, might have several other applications. Slowly, and without much warning, it looks as if Alphabet's life sciences division is pushing hard to get us closer to the future we've been promised by so much sci-fi.