[MetalMan]

Dimension doesn't really have any interest in developing the CAR version. I tried to get them to do it, but they apparently have "better" things to do.
I have the only known CellShield made for car use. It's a beta version, so it isn't perfect. Unfortunately John from Dimension Engineering seemed to stop responding to me while I was testing the device.

As it is, I no longer use the CellShield CAR version. It's got a few problems from what I have found:
-slow response to voltage depression (in cars, voltage depression is quick, and it can't keep up)
-resets as soon as you hit neutral (not a good thing when you potentially have expensive batteries resting on its judgement)

What I do like about it:
-easy to use (no polarity)
-adjustable cutoff voltage from 2v-3.5v
-up to 6s (I only use 5s)
-cheap (mine's a beta so it was free :p )

If you guys contact Dimension Engineering and request the CellShield CAR version be produced, then I can try to continue testing mine and reporting to John to make it even better.