My opinion would be at the point when a reasonable person would fear for their life.

For instance, if I own a vehicle and it is my primary method of escape, and someone starts fucking with critical systems like say the exhaust with a sawzall, I woud definitely start fearing for my life and the life of my family. Particularly when automobile is absolutely critical for survival, access to grocery/medical care etc, escape from say criminals in your yard operating sawzalls in commission of felonies, in much of America. If someone is in my yard fucking with my way to get away in danger, and they're physically tearing it apart with a sawzall, then I think it would be reasonable to allow defense of my family.

If someone is just stealing a hood ornament with their hands, then no maybe it's unreasonable to fear for your life.

With a phone I think it would depend more on context. Intentionally and without consent stealing / disabling someone's method of calling for help and emergency could make a reasonable person fear for their life if that person was also in the process of commission of felonies in your immediate proximity with a dangerous sawzall.