I don't know what Glenn means by the mirror being impractical. I wired a 12V Passport 8500 to my 350Z's mirror power and it worked very well:
http://www.350z-tech.com/forums/141-how ... 500-a.html" onclick="window.open(this.href);return false;
It makes for a very clean install, and if you use quick taps you don't have to break out your iron.