This prosthetic thumb shows you what it's like to have two thumbs on one hand

[Bunbain]

The extra thumb allows you to easily do things like crack eggs, swipe an iPhone, and squeeze a lemon with only one hand instead of two

I watched the video. All those things can easily be done with one hand. Unless of course you are missing a thumb.

created a prosthetic thumb, not to replace a missing digit

Nevermind!