Yes, the kill switch.
I was intending to switch to rain mode but hit the wrong switch by not paying attention. It's not exactly clear to me when the motor restarted. I felt the cruise control turn off then I looked down, saw the ABS light on, thought "I'm still on the bike. That's no bad thing", twisted the throttle and kept riding. I was surprised how little disruption there was. BMW got this right: it is apparently idiot proof.