In an episode of The Big Bang Theory, Leonard, Howard, and Rajesh were designing an app (the Lenwoloppali differential equation scanner) that scans a hand-written (differential) equation and solves it, including detailed steps how to do it without your phone. If I remember well, the domineering Sheldon was removed from the team but he created a great app to find shops with scanned shoes with Penny.
I just saw some hype, downloaded the three boys' app (iOS here), and impressively enough, it just works.
Just try to see what kind of tasks may be replaced by phones – or cheated today.
Well, so far it doesn't do differential equations but you should take a pen, write a quadratic equation, and you will get a solution. Or try a set of linear equations. The equations may be hand-written; and the solutions and steps are written down in \(\rm\LaTeX\) quality and accompanied by insightful, beautiful graphs of some relevant functions. A calculator is a part of the app.
Sets of quadratic equations are too hard – you're told that the app can't do it "so far".
Needless to say, when things like that become common, it will raise questions
1) whether the exams may still be fair
2) whether it's meaningful to teach various things, and how much.
Concerning the first question, I think that smartphones should better be banned during exams – and the ban should be safely enforced.
Concerning the second question, I think that the amount of drill should indeed decrease because various activities may be done by intelligent machines. But the students should learn to do such things in principle, too – and practice them at least "many times" because it's important for them not to be stupider than the machines, and because they must still understand what the machines are doing and catch obvious mistakes etc.