Your Psion machine is Java ready, but how care about Java.
Now you can use a bit more esoteric programming language
called Brainfuck. There is my implementation of Brainfuck
interpreter with name Brainsuck. Idea made this program was
born during breakfast on the Shucon 2007 party with Logout's and
Gasman's moral support.

You can download sources, examples and EPOC binaries here.