Question Gen 3 prius

If you push and hold the button while stationary it will turn off the car, automatically shift the car into Park, and apply the electronic parking brake. If you have it configured, it will also automatically unlock the doors.

I'm not sure what happens if you shut off the power while the car is in motion... it it does all of the above, it seems like it would be a painful (for the car) way to suddenly stop the car.

 

Why do you have your seat close to the steering wheel if you are tall?

Even if the airbag isn't one of the defective Takata airbags that shoot shrapnel, you should be as far away from the airbag/steering wheel as possible, since the airbag deploys at explosive speed. Airbags have been known to break the bones in the forearms of the driver's arm while holding the wheel. So it isn't good to have your chest close to the airbag, unless you want to risk extensive injury, or death, from an airbag deployment in an otherwise survivable accident.

 

Here's something, 2nd gen but probably similar:

 

Since the car is already in Drive when you stop and turn off the power, I don't expect anything different will happen just because the car might be moving. Pressing Power puts the car in Park and shuts down the power.

EDIT: After watching the video that was posted, I take that back. It looks like the button is locked out when the car is in motion. I suspect Gen III design is the same as Gen II.