If you have purchased the full Service Management suite then SLM out of the box is based around a service by service SLA approach. Just have multiple SLA's one for each service with the same timings. That way you can break down reports by service. If you do not publish any SLA's then the system will use the escalation system (ootb priority based)
If you don't have the SLM license then you will have only Escalation which is effectively one timer for all services however saying this it is possibly to augment by service using the exceptions functionality. If you do not have SLM then you will not get the nice dashboards and reports etc.