If you'd been charged with the cell phone statute, your points would be an absolute defense. But you weren't charged with that.
What did you have displayed on the screen? If it just showing your phone idle display or a map or some informational thing, then one could argue you are not guilty. If you were watching streaming video, you're likely guilty.
If the former is the case, this is one time where you might have a good shot at a TBWD, and if that doesn't work go for the trial de novo.

