I assume a book titled "X from scratch" requires no previous knowledge for the intended audience. It's hard to talk about writing apis without knowing the difference between POST and GET
Nice presentation and solid idea. Initially I don't see the advantage over just directly calling the business. Traditional land line phones are loud, and are quickly answered. A messaging app can easily be silenced. If the user wasn't exactly sure what he/she needed I think speaking to someone is much more efficient than describing via a message.
Why would a business not have someone available? This isn't much different from an employee answering a phone, granted in this case it's the employee's personal phone.
I spend more on drinks in one week. And besides there's just something nostalgic about live television you can't (currently) replicate on the web. I can instantly watch programming on topics I would otherwise not seek out myself.