I’m sure this is a great method. I’m f you don’t have your iPhone updated to the iOS 14. I have yet to get the method to work the way it’s explained in the tutorial. More of an Android method than iPhone. Which requires an extra step.
I’m definitely not saying this isn’t worth the small amount being asked. I’m saying that if your device is up to date ( IPHONE ) then I’d wait until there’s an additional resolution.

I almost rated this a 4 because in the video you can't see the phone screen as he is explaining it. However, I gave it a 5 because if you listen to the explanation, you should get what you need to do and the effect is AWESOME! This is something that someone is going to do on TV. I will definitely use this.
KJ

It's an interesting principle, but it should be advertised as iPhone only and even that may be misleading, according to a question on the discussion section. There is also the question of cleaning up, which I have raised in the discussion section, without and answer up to now. This is valid for a borrowed phone, of course you could do it safely on your own phone, but that gets suspicious, I can do an app to do the same and much more.

A truly spectacular effect! I am happy to have purchased it but I have a problem in understanding the explanation because I do not know English very well and I cannot understand the various steps in compiling the numbers on both the iPhone and Android, if a detailed written explanation were possible, even in English I could translate it later with the translator. Thank you

Unfortunately, as is the case for so many magic videos, the instructor has no friends... or at least none that would lend him an Android phone. Also it seems that no one noticed that the phone screen was mostly unreadable during the instruction. Maybe viewers are not worth the time to reshoot a scene or the camera operator did not know how to adjust for the phone's brightness.
The trick, however, could be quite good if performed well. All technique, no app or special gimmick needed. Works well on the phones of strangers, but may not work well on the phones of people who you share friends with.