How can I trust that that push-button ignition will still shut off the car? I know it's conceivable that even a key-start ignition might turn all ignition control over to an ECM, but who's done that?
Saturn and GM did, somewhat. I have a 2006 Saturn ION and you turn the key to the start position and it "automatically" cranks the engine from there.
I hadn't completely shut my door one night and the dome light nearly drained the battery. I turned the key to start and let it go just like normal. The "computer" kept cranking the engine until the car started.
The goal of science is to build better mousetraps. The goal of nature is to build better mice.