I was looking at the car camping trip as just a convenient opportunity to play with the biolite. When driving I would of course use the car to charge the phone. However, if hanging out in a campground, starting the car just to charge a phone would seem like a rather inefficient method?
Perhaps. As noted I recieved it as a gift. I probably would not have bought it on my own.

The biolite could be useful in a couple of situations. Once it gets going it burns hot with very little smoke. I keep it stashed with our emergency supplies at home. In the event of a power outage I can make some coffee or soup, and keep my phone charged. I also have a flashlight that can be charged with a USB. As noted, the main issue is that the biolite is quite heavy.