I apologise for my uneducating comment.

MapComplete is good feature-talking, but it's a web application that's not well optimised for mobile use. I have to say that the only time I've used it is for mapcomplete.org/surveillance.h…?

Opening it on a mobile phone is a very bad experience, even on a recent, powerful phone. The map lags very quickly, clicks are slow to react, and it sometimes took me several minutes to add a single camera.

Surveillance under Surveillance

Surveillance cameras and other means of surveillance

^{mapcomplete.org}