as an alternative to whole frontends like mythtv; which wasn't really designed for car-use; i'm (trying) to use FVWM2 with nothing but the FVWMbuttons plugins - on moose.ca i found some pictures of what i sort of wanted, and moose was kind enough to send me a sample .fvwmrc (which isn't that easy to configure)
the advantage of such a system is that you can use any apps and skin them to fit the theme. i'm mainly interested in gpsdrive, a raster navigation program (alpha support for vector data from OSM is in CVS, so please contribute to OSM to help get free maps for linux)
but one of my remaining tasks is finding an audio player that can easily(!) be used with only a touchscreen (with some predifined playlists, aswell as the possibility of choosing all albums from one artist, and dynamic genre-playlists) if you happen to know something please post it here! if it only does part of the job described, you're still welcome to keep the thread running.
moose uses a skinned version of GQmpeg, which i did not very much like from the point of easiness of use (for a car-p.o.v.), aswell as stability.
maybe xmms2 will join in here once it's a bit more advanced (5 SoC-students working on it)
other suggestions for a wm-based-frontend?