Do we even know what an "outstanding warrant" consists of in China? Granted, I may be naieve about what it represents in the US, but I hope it's something that comes from a reasonably transparent and fair process. In a totalitarian state, it could mean something else.

The question becomes: Who is being rounded up, and why? This seems more important than the specific technology used.

I happen to live in a neighborhood where the very presence of a police officer would attract notice.