I have no interest in carrying a cell phone and being leashed to harassment by customers and employers 24x7. Leave a message on my landline or send an email -- I'll get back to you when I have time, not cater to your impatient demands for instant service impinging on my personal life.
Seeing as I don't want to carry around a phone all the time, what I want is a tablet device that will let me use a stylus to scribble notes and diagrams, a true replacement for pen and paper.
...though his invention worked superbly -- his theory was a crock of sewage from beginning to end. -- Vernor Vinge, "The Peace War"