watch command in cygwin

it is in "procps" package
some common tools, like top, watch, procps, uptime and more

also read this (shell script to create watch() function)
http://www.commandlinefu.com/commands/view/3113/for-all-who-dont-have-the-watch-command

M1:
watch() { while test :; do clear; date=$(date); echo -e "Every "$1"s: $2 \t\t\t\t $date"; $2; sleep $1; done }

M2:

watch() { t=$1; shift; while test :; do clear; date=$(date); echo -e "Every "$t"s: $@ \t\t\t\t $date"; $@; sleep $t; done }