This is what I use my phone for:

Calculus of Multiple Variables

Because I am a lost cause when it comes to 3D drawings (or drawings of any D for that matter), I choose to sit on the front row and take creeper pictures whenever a visual in this class is beyond my ability to copy. It's really an excellent tactic because he's really mastered the art of these things. He draws them near perfection, first try, every time. And I just sit and wonder, HOW?? You need to click on that picture and zoom in and snoop around because it truly is impressive. 

Ladies and gentlemen, this is one of the grandest uses of technology. I just wanted you to know that. 

The end.