I remember a long time ago on an unfamiliar journey I used a laptop and serial GPS plugged into a 12V DC-AC inverter. I ran some mapping software (can't remember what, probably keygen hacked) to give satnav-like routing. I'd say that this was around 2002, before phones were smart enough even to have displays that could be used as maps. Since that didn't have voice announcements at all I don't bother having them turned on in any car.