sms alarm be continuous until msg read?

Hi,

I am on-call and the sms ring tone is max 40 secs. notification doesn't seem to work though I pick 10.

Is there any sms on-call software out there. I switch off all sounds at night, with that apps running, I can still receive continues alarms until I read the message?

or is there an alternative way, so alarm can be continuous until I read the message?

thanks

Andrew