Timer for channels
Add a timer - like an egg clock.
"I set the timer on this channel to 15minutes, and when its over, @channel gets a notification to stop their tasks and message the results here"
"Ok, everybody brainstorm this idea until the channel timer bleeps"
"Scrum meeting is delayed 30 minutes, I set up a timer so you dont miss the start of it"

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cmousset commented
This is already possible using the default slash command
"/echo {message} {delay in seconds}"
although converting your time period into seconds can be a pain. -
Mark Carpenter commented
This would almost be better as a custom slash command, you could do something like
"/timer 30M 'Meeting Delayed'"
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Andrew Letson commented
This would be useful for many members of my team that use the Pomodoro method.