Put 'deb http://scratchbox.org/debian/ ./' in /etc/apt/sources.list
apt-get install scratchbox-toolchain-arm-gcc3.3-glibc2.3
Get kernel-2.4.19
Apply stupid__r1.patch
Apply patch-2.4.19-rmk2
Apply linux-2.4.19-rmk2-5mx2.patch
Apply tim.patch
export PATH=/scratchbox/compilers/arm-gcc-3.3.4-glibc-2.3.2/bin/:$PATH
make mrproper
copy linux-2.4.19.config to .config
make oldconfig
select N for Thumb and the correct keyboard for your psion
make dep
make Image
Mostly this seems to work - I'm having a problem with the poweron/poweroff button