if you have this problem with your child, an app is not the solution. you have serious discipline problems.
Let me clue you into reality. When kids pop out, they are uncivilized savages. It takes a good 25 years (on average) before they stop acting like savages and start resembling a reasonable human being. A reasonable person does not require an explanation as to why answering a call from a parent is important, they just answer it because they are reasonable and civilized and know automatically that answering such a call is the right thing to do in the civilized world. A reasonable person also does not require others to pander to their "preferred method of communication", they just pick up the phone and deal with whatever's on the other end.
Teenagers with phones are like hungry cavemen with shotguns. There has to be a way to pull the plug before things get out of hand and dumb stuff happens. This app is part of the solution. If a teenager's trumped up, uncivilized sense of independence is telling them to disrespect their parents and not answer their call, then this app is a useful tool for parents. The correct mode of operation, of course, is to prompt the child to call their parents so the parents can then tell the child that they're coming to pick them up immediately, and to have the phone ready to hand in because they're never going to see it again. The child should also prepare to have their wings clipped.
Unreasonable savagery can not be made civilized through reasonable discussion. That's why economic sanctions, bombs falling from airplanes, and smartphone crippling apps are still effective tools for civilized people.
Yours is just one data point. Here's another: it's perfectly possible to actually trust teenagers without regarding them as savages, while still catching the bad stuff that inevitably happens.
Different cultures tend to raise their kids differently. Many North American disciplinary actions are downright illegal here. Our kids still turn out fine.
I didn't say I was an expert on parenting. Did I?
Did I also say that teenagers are always and everywhere uncivilized savages? No. I made one over-the-top statement equating teenagers with cavemen, so I guess that's worth pointing out because it obviously proves that my entire comment was wrong, especially since that one statement can't be applied universally across time and space. Jeez...
Look, I've seen more than a few reasonable teenagers, but that's only because I roll with orthodox Catholics who actually believe what the Catholic Church teaches (without whining about it), and believe it's important to teach their kids how to be civilized. It's noteworthy that those teenagers only have dumbphones, if they have a cellphone at all.
So what if different cultures raise their kids differently? How does that negate anything I said? The children of one culture are born just as uncivilized as the children of any other culture. Civilization comes only from hard work. If you're a parent, imparting civilization to the uncivilized requires the right tools. If you're ok with giving your kid a smartphone, then it makes sense to have a tool to reel them back in when they can't resist the urge to abuse the freedom you've given them.
So, go take your pedantic inability to reason clearly, and participate more fully in whatever culture of deficient civility into which you were unfortunate to be born. I'm sure it'll turn out fine.
Today, like in the 1500s, Catholicism saving the world from the "uncivilized savages". Hilarious.
The things you say, they do not hold true across cultures. Sure, things should be developmentally adjusted and it is true that people's brain develops until around 25, but none of this at all makes them savages.
Watch classrooms. Teachers that treat students like savages get savages as students. Teachers that talk in a reasonable way to students (adjusted for kids understanding) tend to have better behaved students.
Sorry, man. Children aren't savages. Like adults, a few wind up bad, but most... nah.
Note that I explicitly and carefully said: "Unreasonable savagery can not be made civilized through reasonable discussion." The only reason that children can be taught to be civilized is because they do have some faculties of reason, and those abilities get stronger with age and appropriate training. When they are young, children learn best by imitation. So, of course, if a parent acts like savage, the child will too.
However, what we were talking about was the appropriate response to those times of "unreasonable savagery". So stop being a pedant, and changing the subject. Is a smartphone crippling app an appropriate tool for a parent to use in response to a teenager who is acting like an uncivilized tool? Absolutely. Is your view on children disconnected from reality? Absolutely. Do you also have wacky views on crime and punishment? I'm going to say yes there too.