Hi,
it happens that a ticket escalates without the person that owns the ticket recognizes it. For example, the person is on a place without internet.
In that case, other people should be informed.
How can I solve this?
Right… What a stupid question 
But to make it less stupid…
What if I want that to be applied only to some Tickets, for example that are tagged as “important”?
Then it would be complicated 
You could set up a trigger with expert mode switched on and then s.th. like “priority: has changed” “priority: high” “tag: important” “group: your desired groups” and then send out an e-mail to those that want a notification with a text where you can use variables to insert the ticket number and other information. Depends on the number of agents and departments you use if this will be useful or not. And before you ask: you can’t check if the owner of the ticket is out of office with a trigger 