I've just started looking into using an Arduino to show the status of a server by simply lighting an LED. So the main logic needs to be on the computer. Obviously the Arduino app will connect to the Arduino board, but is there a C library or something that I can use to create a custom app that will sense when the Arduino is plugged in and talk to it that way? I'm on Mac OS X. I'm pretty sure this is possible but I'm pretty swamped with all the documentation and I'm not even sure what search terms to use to find documentation on this.
To be specific, I'm hoping that I can have a daemon on the computer, it will sense when the Arduino is plugged in, and when it is plugged in, it will tell it to turn on/off an LED. Maybe in the future I'll add a button to the Arduino to tell the computer something, but for now I'll start with just the LED.