for uploading, absolutely use syncthing. you can set it up so that it works in only one direction, i.e. phone to server, so any file that appears on the phone’s download folder gets sent to the server. the one you want is syncthing-fork on fdroid.
as to listening to the music via youtube check out innertune, also on fdroid.
doing WHAT the fuck now?!?
on a more serious note, can you elaborate on the thing where you, a call receiver, have access to the GPS on the caller’s phone? like, how?asked and answered, still don’t understand how that happens.