This service checks that the hosts specified are up (in this case all hosts in hostgroup fionavar)
define service{ use fionavar-service hostgroup_name fionavar service_description net-local-ping check_command check_ping!100.0,20%!500.0,60% }
Note the use of hostgroup; one could also specify a single host, or a comma-separated lists of hosts. Specifying multiple hostnames or a hostgroup results in a line for each host+service in the service details screen.