For arbitrary businesses reaching out to mass-market clients, it'll be a decade at least before "customer is extremely likely to be carrying true smartphone" will translate to "exploitable assumption". Local businesses do not as a rule write cross-platform phone apps. If you want to be the company that e.g. gets rid of those stupid flashing pager things that restaurants give people waiting for tables, it helps you very little to know that 1/3rd of restaurant customers will be holding an iPhone.

On the other hand, that application is more or less "hello world" with Twilio, and presents a fine customer experience even to people with iPhones.