In a previous life I owned an offroad company and have many experiences with building offroad vehicles for most conditions. IMO, essential functions of an automobile should be kept as simple as possible so I'd recommend keeping all of your lights on the tried and true relay/switch design. Might want to take the same advice for your communications.
I suppose you've seen the movie twister? Remember how crazy it was while they were chasin'? Imagine having to reboot shortly before you HAD to notify one of the other rigs in your party that he's in danger.
If you really want to look into this then there are devices out there that connect via USB and can be programmatically turned on and off via software. The only one I could find quick is located here: http://www.dynatorch.com/PortExpander.htm You'll want something like this though this one in particular may not work for your application. You may want to do some searching using the keywords "automation, dc voltage, computer/laptop, etc."
I like the idea of automation and the possibilities...