This sounds possible in theory, but difficult in practice.
Designing a test suite that catches all possible life-critical errors is near impossible. The cost of testing and certification will probably be quite high, well outside the reach of amateurs.
Just as we advise people not to write their own crypto (its easy to get wrong), I think the same will hold for safety critical software.
All that being said, I think it is very important that this software is open source.
I'd love for it to be open source (and I do believe that would be the safest for all), but you know as well as I do that's not the world we live in. The safety code is going to become a feature/price differentiator/trade secret that car companies live and die by.
Designing a test suite that catches all possible life-critical errors is near impossible. The cost of testing and certification will probably be quite high, well outside the reach of amateurs.
Just as we advise people not to write their own crypto (its easy to get wrong), I think the same will hold for safety critical software.
All that being said, I think it is very important that this software is open source.