Probably the same thing that happens after you change your password. Send you an email and if you have some extra level of authentication it would also require it as additional confirmation. I would not be surprised if it would also revoke all active logins. In general, it feels like a pain in the ass to jump all the hoops because your phone moved in a weird way. Just imagine, you ride on a bus or in a car, sudden deceleration happens and you get logged out because their authentication system interprets it as "Someone tried to wrestle the phone out of your hand! WOOP! WOOP! Increasing security measures!" or something like that ;P. Regarding videos, sorry if it seemed patronising to you (and it was not my intention). I've shared the videos mainly because seeing how quickly you can crack passwords and what makes it harder speak to me much more than reading some article, oftentimes filled with unintuitive numbers. Example: Think fast! Your password will take 18500 hours to break. How many years it that? About two years and forty days. One year is 8760 hours. I wondered what would happen if the system failed to authenticate your movements.