Nothing sexy about monitoring. You or I could build our own overnight. Twilio is the true leverage and why they command a much higher P/E multiple

I agree with you but I’d phrase it differently. Perhaps that neither monitoring nor sms is “sexy,” but that you could reasonably hack together a monitoring MVP over a weekend but not a telephony MVP. There’s a natural barrier from the underlying problem domain.

Of course you can put together an SMS sending service over the weekend. It just won't scale to the whole world and will have limited throughput.