Service Level Agreements/Contracts and Activities

I realize that Contract Lines can be used to track time/support against a Contract, but is there a way best to apply a Service Level Agreement (SLA) to Activities?  I would like for us to be able to track time spent in Activities and bill it against an SLA.  I found this article which is sort of what I am looking for, but I need more detailed explanation:

https://community.dynamics.com/crm/b/richardknudson/archive/2012/04/24/user-configurable-service-level-agreements.aspx#.UdMe8vm1Gmo

Any help is appreciated.  Thanks!