"also works for other cameras"
How does it work? Is there an impact sensor built into the hardwire kit so that it can power up any micro USB camera if it detects an impact?
Or does it just send a signal to the camera on one of the USB pins to say that it is in parking mode or full record mode, in which case parking guard will only work with a mini 0903, but it can power any camera as a normal hardwire kit?
An empty battery is 11.8V unless there is a lot of power being used, and if you want to be able to start the engine you will need more than 11.8V in the battery.