GPS Tracking App

Hi, I would love to have an app like: “Once an hour (or depending on the situation once every 5 min) post my phones location on some self-hosted service.” Friends having a specific URL can look up my location in case of an emergency. Extra: In case there is no cellular reception just try again as long as possible. It is for when you are alone in a more dangerous situation and want people to be able to find you. Extra: Also change behavior if panic button is used (Special message on website that button was used at [time] on [location]; more frequent location updates). Do you know any foss app for that? Best, Thomas