Remote Stage Timer

Remote Stage Timer is an iOS timer app used primarily for presenters on a stage. This app can be controlled remotely, but it doesn't require a separate app as the controller. You install a single app, and select whether you want it to be the control or a display (select the gear icon at any time to change the mode). All iOS devices must be on the same WiFi network to communicate. It can take 30 to 60 seconds for the devices to find each other. You can also have multiple displays. Just install the app on all the iOS devices you want to use, and select one device as the Control, and all the others as Displays. It can warn the presenter(s) of an approaching deadline by turning Yellow when getting close, and Red when you are very near the end. Also, you can select what happens at the end of the countdown. All modes will flash 00:00 four times, then continue to one of these options. None - Stays on 00:00. Count Up - Will count up from 00:00 to let the presenter know how much over time they are. Flash - Will flash Red 00:00 continuously to enforce the fact that they need to stop. Clock - Will show a clock with the current time.
A typical setup is to use an iPhone as the controller, and place iPads where the presenters can see them. Or an iPhone on a podium for a discreet timer, controlled by someone else.