Since I had nothing else, I first began using a Blackberry holster with my Droid. When it was inserted right-side-up, it did activate the car app and it did tend to drain my battery a bit quicker.
However, I found by inserting the phone upside-down into the holster does not activate the car dock. Sometimes it does activate the screen, I think because the phone recognizes the magnets for a split second as it is inserted into the holster. If I holster quickly, the screen will remain off (if it was off when inserted).
Just thought someone would find this interesting or informative.