Based on the discussion in this thread doing such a thing seems relatively easy.

Obligatory Orwell:

“The most gifted of [the Proletariate], who might possibly become a nuclei of discontent, are simply marked down by the Thought Police and eliminated.”

That assumes use by a malicious government, but what was described above was illegal use by private entities.

I'm pretty sure that in Germany, some of the described activities could be punished with prison time (and they certainly should).

That's absolutely a chilling effect. Just thinking about this I'm thinking back on events I've been to what what the government can infer from that. And they can probably nail us for anything now whenever they want to and it will be hard to trace it back to this kind of monitoring and analysis. The only way to avoid that would be to leave your phone at home and hope nobody records you or takes photos.

So this is just a way to bulk identify people in a certain location at a certain time. Fairly efficient I guess but could bring up a lot of false positives, like passers by, journalists etc

Then it's going to get very costly for them when the EU goes after some more of that sweet sweet penalty money.