[PeterisP]

Well, if low resolution touch screens are inappropriate for taking math notes past simple fractions, then surely that simply asks for a high resolution touch screens used with a stylus and some system that can convert my equation-like scribbles into proper LaTeX ?

I mean, the main point of digitized writing is not that it's easier and faster - sometimes it is, sometimes it isn't - but that in general you would need the end result to be in a proper, neat format that is useful for distribution, searching, analysis and automatical conversion for various needs; handwriting or pictures of handwriting can be useful for that only if/when it helps you to get to the final formatted non-handwriting end result faster than a keyboard and a mouse does.