Many newer head units have very long boot times, often 20-40 seconds. I would like to do one of three solutions.
1. Wire the head unit to be always on. The amps will turn off when the car turns off, but the head unit will remain powered, even overnight. This will obviously drain the battery, maybe in just 2 hours making this solution impossible.
2. I have noticed that when I unlock my car, the dome light turns on. Perhaps I can wire the dome light to the head unit to get the boot up process started sooner, as I am sitting down instead of after turning the key. Again the amps would still be switched by ignition power. Obviously this would make the head unit turn off when the dome light then goes off. However, I can build a small arduino circuit and write some software to sense the dome light and turn on the head unit, leaving it on until it senses the ignition turn on, and then off later.
3. Some other more awesome solution such that when I glare sternly at my car from across the parking lot, the head unit starts booting.
Has anyone tried anything like this? Any suggestions? I am also considering putting a tablet in the dash because they can go to sleep, and wake up instantly. I am less interested in this option, but still open minded.