To have smsd start at boot time, you have to adapt
${SYSCONFDIR}/smsd.conf and insert the following into /etc/rc.local.

if [ -x ${PREFIX}/bin/smsd ]; then
	install -d -o _smsd /var/run/smsd
	echo -n ' smsd';	${PREFIX}/bin/smsd
fi

smsd needs access to the serial port; this can be done by adding
the _smsd user to 'dialer' in ${SYSCONFDIR}/group.