Triggers

With the trigger armed, a press of a volume button starts recording without any contact with the screen. iOS would normally throw its volume overlay up over whatever is displayed; while the trigger is active that overlay is suppressed, so nothing flashes across the black panel.

The point is the gesture. Reaching for a volume button is something people do in front of other people all day without it meaning anything. Combined with blackout, the phone can be in a shirt pocket or lying on a table and the recording starts from a movement nobody reads as a movement.

Auto-start begins recording a set number of seconds after the app launches, with no interaction at all. Paired with the Reduce White Point shortcut, one press of the Action Button dims the display, opens the app and starts the clock, which is useful when you already know you are walking into something.

One pulse when recording begins, two when it ends. There is nothing else to read, and nothing else to check.