beat me to it, I develop www.jasymchat.com which is based on Jasymca (http://webuser.hs-furtwangen.de/~dersch/)..I was thinking of porting Jasymca to a Javascript.
A Mathematica style program for tablets that could convert handwritten math using common notation into symbolic constructs would be absolutely amazing.
Computers have advanced but calculators haven't.
Calculators are only focused on school kids, not on people who really need to get things done.
I'd love to have octave or scipy on a piece of dedicated hardware.