As I said earlier in the post, SmartActions is not sufficient when you want to choose between two docks, home and car. SmartActions with a GPS rule wouldn't work either because my car is in the garage two floors below the bedroom.
Regarding these "pins", it seems that the micro-usb spec (Micro-USB connector pinout and wiring @ pinoutsguide.com) shows that there are 5 pins. It appears as if pin 1 is for charging, pin 2 is data in, pin 3 is data out, pin 5 is a ground. This leaves pin 4 which is documented differently than the rest as "Mode Detect. May be N/C, GND or used as an attached device presence indicator".
I'm not too good with electronics but I wonder why pin 4 works when that car dock is plugged into the phone but the other end of the car dock is not plugged into anything?
I think we need someone with some electrical knowledge as to how this all works.
Right now, I'm interested because there don't appear to be any reputable dealers out there selling smart cables separately and the ones that do have no reviews or detailed specs. For example, how do I know if I have the cable with pin 4 set to home dock or car dock? How do I know I'm not just getting a random charger cable?