... simply use

while : ; do echo "My command here"; sleep 2; clear; done

or more sophisticated as function to put in .bashrc

function watch() {
  local args
  local time=1
  for args in "$@"; do
    case "$1" in
      -n)
        time=$2
        shift 2;;
    esac
  done
  local infoStr="Every ${time}.0s: "$@"\t${HOSTNAME}: "

  clear
  if [ $# -eq 1 ] ; then
    while : ; do echo -e -n "$infoStr"; date; sh -c "$@"; sleep $time; clear; done
  else
    while : ; do echo -e -n "$infoStr"; date; "$@"; sleep $time; clear; done
  fi
}