However, that by itself doesn't mean you can't collect it, just that you need to have specifically asked for their informed consent and not hidden this purpose away in a changelog.

Does GDPR generally allow you or your apps to collect information that helps identify legal and moral transgressions around you?

What if you are watching the game at a friend's house? The collection is definitely going to have some false positives.

In that case the coordinates would identify your friend.

It seems like deputizing devices to spy on others. Regardless if those others may be doing something wrong or are caught up by accident, it seems like the sort of thing data protection would prevent.

This will be a good test of real competing interests. I don't know that privacy should win in the end here, but both sides actually have powerful prima facie cases to make.