I thought of this immediately when watching the keynote, but then they mentioned they used GPS technology, and I figured they would be passively monitoring to confirm that for the past X minutes the phone has likely been in a car (non-walking speed + on roads).

Clearly they aren’t doing enough of that if you can trigger this after waiting in line in a roller coaster park. I suspect they may end up geo-fencing known problematic areas as their algorithm doesn’t seem as great as they claim.