>>knowing the Twilio API and looking at this design I think someone could build this in about a day.
I don't want to shit on the idea, but with the amount of "build this thing with twilio" content twilio puts out, the benefit of this is saving the time of setting something similar up for yourself.
Don't get me wrong, I wasn't trying to debate buy vs. build. Although if I was going to buy there are much more robust services also built on-top of Twilio.
Just the op asked "what makes this different" and I was pointing out that the barrier of entry is very low.
With that said, if you already know the Twilio API and you already know AWS Lambda + API Gateway + DynamoDB it might be worth it to build because:
1. It would be extensible for your needs.
2. It would be a heck of a lot of fun if you enjoy that sort of thing.
Edit: I can speak to point #2 personally. I have done it. It is a lot of fun... especially for a developer who usually lives in a web browser... to be able to call a phone number and hear the result of your code. It is very satisfying. Much like building an Alexa skill is or finally getting that LED display to light up on your breadboard and print something.
>> It is a lot of fun... especially for a developer who usually lives in a web browser... to be able to call a phone number and hear the result of your code.
That really is the key. I've built some stuff with twilio simply because the delivery method of my code is somewhat unique.
I don't want to shit on the idea, but with the amount of "build this thing with twilio" content twilio puts out, the benefit of this is saving the time of setting something similar up for yourself.