Does this work in the background, or do you have to have that app running?

For a while I was using an iOS app called BuzzClock. I liked the feature that it would give a different # of buzzes as you went through the hour. I found this helped reduce the need to check the time when I was heads-down on some work, or give a subtle reminder that I might be lingering too long on something.

But having to keep the app in the foreground ultimately killed it for me.