StageTimerDisplay for iPhone/iPad is a free companion product for the Mac application StageTimer (available in the Mac App Store), it does not work on its own. This application allows any number of team members to keep track of the timers on the stage monitors during a presentation.
Furthermore it lists all pre-programmed timers, which could be used as a running order.
The macOS application, StageTimer (also available in Apples AppStore), broadcasts its presence, so no configuration is necessary on the iPhone/iPad end.