Creating alerts and escalations before SLA violated

Creating alerts and escalations before SLA violated

Hi guys, 

I kindly wanted to ask how I can create alerts before SLA violations. I also want to escalate it to upper levels. Here's the example scenario: 

I have 3 hours SLA for the first response time and 12 hours SLA for resolution time. My ticket is created at 09:00 - which means my SLA will be violated at 12:00. I need to act before 12:00 comes in. 
  1. 30 minutes left before my first response time SLA(11:30), I kindly wanted to inform person x 
  2. 20 minutes left before my first response time SLA(11:40), I kindly wanted to inform Person X's manager, Person Y 
  3. If my agents respond correctly and 2nd SLA begins counting, I want to use the same scenario. 
How is that possible?