you could tap into the mirror if you have the self dimming one, a kit like the one linked gives you an usb port up there. I plan to do that for a dash camera. Someone here has a thread and short vid on how to install, super easy.
won't be switched though. Alternatively I guess you could look for the wire for a lightbar if you have the aux switches. There's one wire pre run up to either the left or right top of the A pillar. Then you could use one of the switches to turn the detector on and off. Videos and info where that cable is should be easy to find here and on youtube.