Comment by overhead4075

A bit fancier than my awk version

  awk -W interactive 'BEGIN { t = systime(); } { u=systime(); if (u - t > 1) { printf("= %s %ds =========\n",strftime("%T"), u - t); }; print $0; t = u; }'

Or if you want to clear the screen too

  awk -W interactive 'BEGIN { t = systime(); } { u=systime(); if (u - t > 1) { printf("\033[2J\033[H= %s %ds =========\n",strftime("%T"), u - t); }; print $0; t = u; }'