What!? I'm not following your logic. If there is a warrant for your arrest, and law enforcement is tracking your phone, law enforcement can simply come pick you up in a squad car.
Do you actually think there are sufficient LEOs to run around chasing phones for every petty outstanding warrant? Why bother even trying when they can just be delivered by a robot.
Cities are ringed with rich suburbs with overstaffed police departments full of bored cops. I can see them being very interested in a product that scrapes cell subscriber and location data to ID people with outstanding warrants.
I fully agree with you that there's aren't sufficient resources to track down every deadbeat that failed to show up in court, or accumulated too many parking tickets or whatever. However, things that make it easier and cheaper to find people do not bode well for free society. Think about the kind of sigint that went into catching Bin Laden. Now imagine a world where 99% of that is automated and the police feel it's reasonable to use it to catch petty thieves.