Esta página explica como executar um aplicativo GUI usando cron :
To run GUI application using cron in the command section replace the command name part the following way
env DISPLAY=:0 gui_appname
The
env DISPLAY=:0
portion will tell cron to use the current display (desktop) for the program "gui_appname".For example to run the rtorrent client(A terminal based popular torrent client in Linux) the crontab looks like this
# m h dom mon dow command 47 09 18 11 * env DISPLAY=:0 gnome-terminal -e rtorrent