I wired mine to the switched 12v from the radio harness. Comes on with ignition and running the wires was easy. Of course, I did it the same time as the radio so I wasn't going through extra steps.

Definitely run the wire behind the plastic on the windshiel molding. Only a few screws hold it on and it just snaps off.

As a tip, don't put it low to try and be stealthy. Stick it right below the rearview. That way it's as high as possible and the rear element has a direct view out the back window. The higher it is, the sooner you'll detect a threat if you're on changing terrain.