iOS & macOS Limit Timer Software
Easy to handle.
The digital clock on the iOS devices indicates an expiring time:
white (ablaufend), yellow (note for speakers), red (over time)
Up to 999 iOS devices (as of iOS 9.x) can be connected to the macOS server software via WiFi (UDP must be activated) (iOS app is free)
Presentation of text messages (preset or free text)
Functional control over all devices (battery level, device name, displayed time on the device)