dropbox_monitor.sh

#!/bin/bash

#
# "nohup THIS-SCRIPT-WITH-FULL-PATH 0<&- &>/dev/null &"
#

WE_STARTED_IT=0;

while true; do
  sleep 1;
  IDLE_SINCE=$(xprintidle);
  if [ $WE_STARTED_IT -eq 0 ] && [ $IDLE_SINCE -gt 300000 ]; then
    dropbox start;
    WE_STARTED_IT=1;
  fi
  if [ $WE_STARTED_IT -eq 1 ] && [ $IDLE_SINCE -lt 300000 ]
  then
      dropbox stop;
      WE_STARTED_IT=0;
  fi
done