If it&#x27;s programmed defensively, it could be reasonably safe. For example, I would want the car to be performing an ongoing, end-to-end verification of the finger&#x27;s continued presence on the phone.<p>This could mean, for example, the app could heartbeat the finger&#x27;s presence multiple times per second. The car would be continuously checking, such that if 500 or 1000 msec had passed since the last end-to-end verification, the car stops.<p>You could even reduce the risk of API&#x2F;digitizer errors and require the user to continuously tap&#x2F;stroke&#x2F;rub&#x2F;swirl the deadman switch button, or perform some device movement captured by the accelerometer.