I never perceived this could even be a possibility, I recall reading this in a bad sci-fi novel once and I thought it was dumb for a multitude of reasons:

1. It's extremely unlikely that there would be any benefit. Most people would have their devices in a bag or pocket.
2. In cases such as an event where a terrorist attack occurred, there would likely be people recording it anyway and likely happy to had over their footage anyway.
3. There is no piece of software out there which could accurately determine what devices are in a particular area.
4. There is no government dumb enough to propose or support the ability to monitor citizens like this unless they are already in, or close to being in, a dictatorship.

And yet the justice minister thinks it is positive that this would "only be used dozens of times a year"

WTF.