it will end up as a cat and mouse game surely poeple who are up to no good, would just turn off their phone - possibly taking the battery out or placing it in a foiled bag. or give it to another person or even hide it somewhere else doesn't seem very hard to circumvent
But then there's the flip side of that, which is that if you always have your phone... except when you're up to no good, the courts could potentially use that to indicate that you planned on going out for no good.
It's a far better habit to regularly leave your phone at home somewhat randomly. I no longer take mine into town every time, half the time deliberately, half because I just legitimately forgot. I've de-fanged my phone, leave it on the counter instead of in my pocket, and have moved back to a flip phone (week long battery life!), so it's not that much of a loss - but I've had to work to get there. 6-7 years ago, realizing I'd left my phone behind was very much a panic moment. Even though I grew up before them.