I have my HID triggered by the brake light.
It is pretty hard to get very far without touching one of the brakes. it is set up so that once on it stays on till the ignition is turned off.
I had looked into options of triggering off the side stand switch, charging voltage, a separate manual switch, the neutral light, even spark detection, and of course a simple 10 second delay relay. For me the brake light was the easiest and most reliable choice.