The car in that video had so much extra custom stuff it's not even funny. And while it's still a technical feat, I don't see every mercedes being sold with that equipment in it already.
The reason this is amazing is because Tesla is planning on switching this on for all of their new cars in the very near future. It might not be the most technically advanced, but it's here.
While the others make promises, Tesla's making cars.
BTW I doubt that the Tesla is ASIL D complient in this sense. AFAIK their is no ASIL D implemented component right now. Everybody avoids that. But this is required to be fail safe.
The Tesla video is a bit more exciting, because it is using a car that consumers are already driving, whereas the Mercedes has "aftermarket" sensors and a computing platform built in. Mercedes is impressive on the other hand, because that was three years ago.
Having a working implementation in a consumer grade car is impressive, but the ability itself is not novel.
http://www.caranddriver.com/features/semi-autonomous-cars-co...
I could see the former being useful during development, but I wouldn't want a "slam on the brakes" button in my car. And the latter could be much more easily worked out by just switching under any driver input on the steering wheel.
They just kill the engine and disconnect the battery. It's a legal requirement. Nothing fancy.