Would the autopilot be able to land everywhere? Someone said above that it worked on large airports but airports can be different and with different sizes, etc. And maybe it could cause problems for the airport if they weren't ready.
And if you can send information to the plane to do that, or to say it can't land there, can't there be the risk of it being used to hijack the plane? : /
Unfortunately no.
How the system works is, a signal beacon is placed in the beginning of a runway and the autopilot aims for it. If you miss it and try to land a passenger jet on a field you will crash it because the gear is not made to handle rough terrain.
What is more the autopilot won't land by itself. You still need to manually choose the beacon, reduce speed, operate the gear and flaps and after touching the ground reverse thrust and break.
What about a modular construction, where the whole seat groups of 3 are ejected with a common parachute...
Might work, but you'll still need someone to operate the system. Who would that be? The pilot? The flight attendants?
Where would the button be? If we put it outside the cockpit a rogue passenger could eject everyone. If inside, it would make it easier for the pilot to kill everyone without crashing the plane. He'd just have to push it somewhere over the Arctic Ocean and they'd be all dead of hypothermia within an hour.