Let's say someone sees a parking warden they find physically attractive. They follow them for a bit and when they write up their next ticket, the stalker pulls up this app to get the officer's ID. The next day they pull up the app to see where the warden is working that day - they drive over there, and it takes them maybe half an hour to find the warden based on the lag between last-ticket-location and real-time-location. They strike up a creepy conversation and the parking warden eventually leaves, disturbed. The next day, the parking warden is working a night shift - they've been told to patrol a dark neighborhood where there are plenty of alleyways that nobody can see into...
See where I'm going with this?
Anything which allows someone to get ongoing location data for a person who they've just come across on the street is inherently a danger to the surveilled person.