Companies can't track your thinking. They can know when you're using their equipment. I'm fine with them owning what I do with their hardware, networks, anything they pay for... but they can not own my off-time, and they most certainly do not own my mind.

What I build in my offtime is mine; this is in fact where every entrepreneur starts. What you're proposing is that all innovation should stay in the hands of the employer, and you as an employee are shackled at all hours.

I know that some states have different laws in this area, but CAs are strong, and no one owns what you do when off from work and using your own equipment but you. Do not ever give up that right or we all lose.