Thanks Jasper, but this doesn't really solve the issue. Let's say, for example, that my ISP goes down at 2am. If it's out for 5 minutes and then comes back on, I don't need to be awakened in the middle of the night. There's nothing I could do in those 5 minutes to fix the issue anyway. But if the ISP drops at all, even for one minute, during business hours then I want to get alerted right away. Similarly, if the ISP goes down for 30 minutes overnight, then I'd want to be alerted and wakened, not just receive a text that I'll miss.
If I configure this the way you're saying, the power could go out or the ISP could drop at 2am and remain out for hours and I'd never know, because I wouldn't receive a call until business hours the following morning. It's way too easy to sleep through email/text alerts, which is why we configured phone calls in the first place. What I'm really looking for is more flexible alerting so that I have one response during "core hours", and another during "off hours".