https://twitter.com/HawleyMO/status/1180214941867036672
It's important for the discussion that this app does not violate any local laws in Hong Kong. It is a safety tool. You can check out the web version here (click icons and paste text into Google translate if you can't read Chinese) https://hkmap.live/
In a nutshell, it shows where police are (puppy icons), police vehicles, concentrations of demonstrators (construction worker icon), sightings of the special riot squad called the raptors (dinosaur icon), and places where demonstrators can find safe transport (house icon).
There's a lot of rumor flying around Hong Kong that selective website blocking will be the next emergency measure after the mask ban, so it's very important to have a backup version of this site on the app store (and Google store) in addition to the web version.