If I understand u right, u want to hard wire ur radar to ur rear view.
I know a few people that hardwired there radar via the auxillary outlet, but they did not recommend it after they were pulled over lol. Cops dont like when u speed with a radar detector, also, u dont want to just leave it up all the time becuz someone will break in and steal it. Just use it when ur driving and put it away when ur not.
But if u really wanna hardwire, ur gonna have to splice the cord and hook it up to a +, -, and ignition wire. Pretty simple.