I had this installed in my previous vehicle (Mazda5). Looking to install in my "new to me from my wife" 2004 Prius w/ the JBL audio. From my searches I understand I can tap the rear speakers from a wiring going back from the doors. The battery is easy to locate as is the ground. The only thing I am not sure of is the switched power source. I used the cigarette lighter in the Mazda. What are people using in the Prius? I plan on installing it in the cargo area. I always use the cargo cover so theft is not an issue for me. I might try installing it under the cargo shelf/above spare tire.
