The Jetpack has become more secure and lightweight, and has begun to comprise part of Special Services equipment. With its help, you can manoeuvre in anurban environment and react quickly to emergency situations.
I see law-enforcement as a combination of human (possibly with jetpacks... but only after extensive testing and safety considerations and anti-abuse precautions are put in place), robotic (which are already in use), and drone technologies. I also find it highly plausible that out of the three possibilities, one may overtake the other.
How long would the fuel/battery last? I do hope the authorities don't hog the technology and we can buy jet packs commercially (at least up to a certain thrust threshold). And if you're worried about security, well that's a whole not market of arboreal security that just started up!