look like you could use linux at
command. Create a bash script containing something like this, replacing /path/to/pidgin
with your actual path (you can run $ whereis pidgin
to find out the location):
at now + 5 min <<_EOF_
DISPLAY=:0.0 /path/to/pidgin
_EOF_
check out Files and scripts that execute on boot to see where you can place that file.
cron
would be another option