This is the same thing that I do in my maths and sociology classes! Not only does it help improve dexterity, but it forces me to re-type my notes so that they are legible and, as such, study. What a concept, that studying. ;)
How to become ambidextrous
"For some reason, I thought this exercise would make my handwriting neater. Sadly, it didn't. However, it is a cool trick to surprise with. "
How I did it: I was motivated by the fact that people I knew already could do this, with even better penmanship than my original hand. So, when listening to lectures, instead of taking notes, I practiced with my right hand. I also started writing notes with my right hand, since no one else was going to read them and I probably wasn't going to go over them anyway.

