Very easy, without any fancy bells and whistles, but I need to dump this somewhere so I have it handy next time I need it:
New file /etc/systemd/system/saprouter.service
[Unit] Description=SapRouter After=network.target [Service] User=smdadm Environment="SECUDIR=/usr/sap/saprouter" "SNC_LIB=/sapmnt/SMD/exe/libsapcrypto.so" ExecStart=/usr/sap/saprouter/saprouter -r -K -T /home/smdadm/saprouterLog/dev_router -G /home/smdadm/saprouterLog/log -R /usr/sap/saprouter/saprouttab ExecStop=/usr/sap/saprouter/saprouter -s [Install] WantedBy=multi-user.target
And then move on to a simple systemctrl enable saprouter.service