Back in the "old days," medical students and residents often relied on a pocket book and they referred to this as their "second brain" or "peripheral brain." This little book contained all the vital formulas, charts, tables, and clinical pearls that would help you survive the wards (and outpatient care as well).
Now, students and physicians rely on their smartphone as a second brain. The medical smartphone often contains critical medical apps such as drug references, medical database, medical calculators, conversion tools, algorithms, and much more. Plus, with a smartphone, you can easily get online. Once you have access to the Internet, then your brain is almost infinitely smarter (well, as least mine is).
So many healthcare professionals now depend on their smartphones. They couldn't live without their phone. They would feel naked - almost as if they're missing half their brain.