I'm getting close to putting my first Arduino project where it belongs - in the car.
The biggest hurdle for me at this point is power - I plan to primarily use power from the car (12-14v), but I'm also intending to use a key-on switched line - making it a lot more difficult for me to drain the car battery by leaving the Arduino powered on. But, since that's the case, I'd like to have a battery backup - in case I want to turn the car off, etc. Don't need to recharge the battery from the car power, just a simple 9v will do fine.
With a little bit of research, this is what I've been able to come up with. Any glaring problems?