SMTP (aka email)
>"Maybe there's a way to set up notifications for only certain messages..."
Yes, he could run a background process that sifts incoming emails for a specific string, and then have that process sound an alert.
In fact, I would not be surprised if some email clients already have that capability built in.
@Pat @marcorobotics If he doesn't have notifications turned on, he might not see it for hours. If he does, his device would never stop screaming.
Maybe there's a way to set up notifications for only certain messages...