Working with a lot of principals at conferences, I have seen people mention about checking in on their phone because they might be worried about what is happening in their school. Just like any part of education, people have to leave for professional and personal reasons, and they cannot physically there. That being said, if you think as a principal, the school could fall apart without your presence, you might not be doing one of the most important parts of your job; developing leadership.
If you have created a culture that builds leadership, the majority (if not all) of emergencies that happen in school will be handled by the people in the building that you have entrusted with kids. Great leaders build cultures that are not dependent upon any one person.
So if you are checking your phone over and over again, to make sure nothing is going wrong at the school, you have some work to do. Supporting people is important and I know many leaders want to be available to their team, but developing people and trusting them is crucial to the success of any school.