Stable that is "on" all the time? I am not aware of something like that. The reverse light will be on only when you are in reverse gear. The break lights will be on only when you are pressing on the break pedal. What do you need that for? How many amps?
This question is related to my other question regarding the reverse light. Reverse Cam.
what i wanted to do is use a relay in which i connect the reverse light + and - to the trigger of the relay, and the + of the camera i connect to a stable 12v through the relay.
with stable i mean - it doesnt go down to around 10v when turning the steering wheel.