Vernor Vinge introduced some interesting input options in his novel <a href="https://www.amazon.com/Rainbows-End-Vernor-Vinge/dp/0812536363" target="_blank" rel="nofollow noopener noreferrer">Amazon.com</a>. Us older people could use a keyboard interface on any surface. Younger kids were learning the fidget interface so they could covertly text each other in class by fidgeting. That way it was difficult for teachers to tell if they were texting or really just fidgeting.


If you don't mind me going OT on this one (we're in the general area, after all), the fidget interface reminded me of the real language that prisoners of war in Vietnam invented to talk to each other as reported in <a href="https://www.amazon.com/When-Session-Admiral-Jeremiah-Denton/dp/1935071157" target="_blank" rel="nofollow noopener noreferrer">Amazon.com</a>. I can't remember exactly, but they called it something like the cough, hack and sneeze language. Respiratory infections were so common that guards couldn't tell if they were chatting with their friends (which was forbidden) or really coughing.