ok to answer my own question for future reference...

I ended up running the wire down the A-pillar to the 12V socket below glove compartment. That 12V socket does get switch off after door is locked, just not immediately. Manual says power will be interrupted 30 minutes after ignition off, which I confirmed works. So I'll just leave it there until I can find a 12V source that will switch off immediately.

 

In all honesty, it will hardly affect the battery during those thirty minutes if at all!

 

Nice. Did you have to purchase a special/additional cable to do this? I assume to mounted it up by the rearview mirror? Do you have any pics?

Thanks

 

Yeah I also don't think 30 minutes draws enough current to kill the battery.

I was actually mounting an Escort (with factory suction cup). Just spliced my own cable.