screen -ls | grep tached | awk '{ split($1, x, "."); print x[1] }' | while read i; do xterm -e screen\ -dx\ $i &; done

sh -c 'n=0; while true ; do  echo n=$n ; screen -x -X select $n ; n=`expr $n + 1`; if [ $n = 4 ]; then n=0; fi ; sleep 5 ; done'

(from hubertf@)