[Spieder]

For those of you with hardwired radar detectors, where are you accessing the power? I wired directly into the power rear view mirror wires on my i3 but wanted to double check before I started pulling the overhead console apart.

 

[EV_technician]

I would advise on running power from 12V battery if possible. BMW is known for so sensitive ghost protocols that look for any unusual conditions.
On the other hand if you looking for hardware to be powered on only when you have EV on, your idea is ok.