For that you can create a timer which sends the message in 30 minutes everytime someone sends a message, by naming the timer it'll overwrite itself and reset the 30mins counter:
on *:text:*:#yourchannel:.timerresetcounter 1 1800 msg $unsafe($chan) This message is sent because nobody said anything for 30minsIf you want to stop that, just use "/.timerresetcounter off"
