This is cool, but I'm having a hard time seeing this working in a real product.
Guitarists have been using their picking hand or pedal controls since the beginning of the electric guitar without much fuss or concern.
I also thought pie menus died off because everyone decided they were too limited, hard to understand, and overall annoying regardless of the input method.
Ha ha, you must not be aware of graphics tools like Blender, Maya, Rhino, Krita, SolidWorks, etc, or games like The Sims, Secret of Mana, Neverwinter Nights, Crysis, Mass Effect, Battlefield, etc.
"Hard to understand" is on you, buddy. I wasn't aware that "everyone" got together and agreed on everything -- that seems like a suspicious claim. Where did you read that? Surely you can cite some papers and article by "everyone" as evidence, and you're just not making it up in an attempt to troll.