Google shows a special card when you search for [metronome]. The default beat rate is 120 BPM, but you can change the value from 40 to 208 BPM by pressing the "+" and "-" buttons. Google plays a sound, shows an animation and changes the color of the UI, depending on the selected value.
According to Wikipedia, "a metronome is any device that produces regular, metrical ticks (beats, clicks) — settable in beats per minute. (...) The metronome is used by musicians to help keep a steady tempo as they play, or to work on issues of irregular timing, or to help internalize a clear sense of timing and tempo."
{ Thanks, Mukil Elango. }
