Check if /var/run/reboot-required
exist.
cat /var/run/reboot-required
*** System restart required ***
You can also check reboot-required.pkgs
.
cat /var/run/reboot-required.pkgs
linux-base
dbus
You can edit you startup script to perform the check.
if [ -f /var/run/reboot-required ]; then
cat /var/run/reboot-required
fi