This APP is only applicable for Portugal
Send a complaint about illegal parking to the relevant authorities, under Article 170(5) of the Portuguese Highway Code (source: https://diariodarepublica.pt/dr/legislacao-consolidada/lei/2013-116041830-116043580).
However, this application has no affiliation with the police or any state or government entity, having been developed by a private citizen with the sole purpose of allowing citizens to report illegally parked cars to the relevant authorities.
The police confirm that they follow up on complaints from citizens through this channel (source1: https://poligrafo.sapo.pt/fact-check/e-possivel-denunciar-o-estacionamento-indevido-de-carros-atraves-de-uma-aplicacao-para-telemovel/;
source 2: https://www.dn.pt/arquivo/diario-de-noticias/carro-mal-estacionado-ja-pode-fazer-queixa-com-esta-app-8686600.html).
The app already covers all regions of the country and detects a range of parking violations, such as cars parked in disabled spaces or in front of traffic lights.
This app is completely free, ad-free, and its code is fully open and shared (source: https://github.com/jfoclpf/form-for-parking-violation).