For chewers, crates work really well too.
I was surprised to learn yesterday that a regular premier "sure-fit" harness is safe for the car (as well as for walking, tracking, etc), if you buy the harness extender (scroll 1/3 down the page): http://www.premier.com/View.aspx?page=d ... lars/other
We seem to accumulate equipment, but the basic harness remains a useful tool: if you clip the leash to the front of the harness (on the chest of the dog), it acts like a sensible front-attachment harness, discouraging pulling by using the dog's weight to leverage her around to face you if she pulls. If you clip the leash to the back of the harness, then the dog gets to pull comfortably (good for tracking, light scootering, etc), and now it turns out you can use it for cars as well.