Thanks to these instructions I got my radar detector hardwired to the dome light and so far it works great. It’s pretty simple to do once you know how to open the dome light and which wires to tap to in the F30.
The wire I tapped to for power was the white with the red stripe, which is on the long single row connector and I believe that it was the third wire from the left. For anyone who is going try and use this wire I take no responsibility so do it at your own risk and I highly advice to test that wire in their car with a voltmeter. In my car (2013 F30 w. Nav) this wire provides a 12v (~13.5v to be more accurate) delayed switched power similar to the cigarette lighter socket. It can be a bit confusing coming from an E90, when I first got the car I thought the power from the cigarette lighter socket never goes off, but in this car the power turns on when unlocking the car with the remote and turns off I believe about 2 minutes after locking the car so it seemed that the power is always on.
As for the rest I followed the same instructions as in the E90 DIY:
http://www.e90post.com/forums/showthread.php?t=97545.
I didn’t take pictures when I did my car, but I’m going to do my friend’s car next, so I’ll try to take pictures and post them when I get the chance.