stagetimer.io - Remote-controlled countdown timer
If you have to time an event or meeting, then stagetimer.io can help. It allows you to create timers and control them from other devices. You can then share a fullscreen timer with presenters and the agenda with participants via link.
stagetimer.io (Beta) - Free web-based countdown timer with remote control
Put a timer in front of your speaker and control it from a computer or phone