Nanotech is on the rise, I wouldn't be surprised to see pills with embedded stuff become common the next five or ten years.
We got a chip put in our cat. Perhaps this could be used for your secure cat door? You could probably use the same thing for humans, though it was stinking big needle they used to implant it.
Don't worry about car systems, ever year there is something new, the stuff that's ten years old becomes completely obsolete.
Current law requires automobile manufacturers to provide repair parts for their cars for ten years. After that you are on your own. I suspect this results in very high scrap rates for cars over ten years old. Computers are the problem. They are unique to make and year, no one but the manufacturer carries them. So here's another million dollar idea:
The universal replacement computer for older cars. It would take a substantial engineering effort, but there is probably lots of expertise available in this area. They've been putting computers in cars for how long now? Ten years? The basics are all the same, naturally there would be variations.
11 hours ago