What is inactivity monitor

[Basha4]

What is an inactivity monitor? 

how do you use it?

Please tell me any real-time scenario.

[Mike_R]

It's really just another method for tracking incidents that haven't been updated in a while and then send out an email to escalate.

This is a good write up here

https://www.servicenow.com/community/developer-blog/get-active-with-inactivity-monitors/ba-p/2267535

We personally do not use it because we already receive emails when SLA reaches 25%,50%,75% and when it breaches. But i do think that the inactivity monitor could be useful for certain orgs.