Marble can do voice nav, though it doesn't override mediaplayer so if you're using the FM transmitter to play podcasts or suchlike on the car radio you won't hear it.

I'm trying to get extkbd set up so I can use an old n900 with knackered SIM connector as a computer n my big screen via tv-out and SCART adapter.

If you have a UK proxy you can use a combination of get_iplayer and alarmed to download all the BBC content you want for later perusal. I also use alarmed with the command line of gpodder to get all the podcasts I'm subscriber to overnight when my wifi is unlinited.