Hawk-Eye is a collection of technologies that allows high-granularity sports tracking, most notably in tennis. It's similar to what we see with basketball, football, soccer, and basically every sport where a lot of money is on the line. That means there's a lot of data to analyze gameplay these days.
The New York Times uses Hawk-Eye data to examine the serve. More specifically, they look at the fastest serve in tennis — coming at your face. Don't blink.