/Silence

Can you implement a command that lets users send messages without the other user getting a "popup/pling". 

I offen want to send my friends messages that they can read when they got time, but i dont want to "pling" their phone when they are at school etc. do you think you could implement a /silence feature that would mage the message not make a "pling" sound or make a poppup

TL;DR: forced DnD on a message