The toolchain can be downloaded from the GPL page of the tomtom site (see the links section).
The installation is simple : extract the toolchain in /usr/local/cross and add to your environnement variable PATH, the following folder :
export PATH=/usr/local/cross/gcc-3.3.4_glibc-2.3.2/arm-linux/bin:/usr/local/cross/gcc-3.3.4_glibc-2.3.2/bin:$PATH
Building MPlayer for TOMTOM GPS is explained here.
My port of MiniGUI to the tomtom is described here.
And finally, an interface to mplayer using my port of MiniGUI can be found here.
