* configure types backup targets ( local network reachable/globally reachable )
* use GPS to determine if the target ( local network ) should be reachable ( it makes no sense to attempt to backup to a server located at my house at 4am if I'm travelling )
* backup at settings to trigger backups only at a specific time
* support multiple synchronization polices such as updated file on a mobile will update a file on a target, but updated file on a target would not update a file on a mobile and reverse ( preferably including separate support for policies on deleted files ), preferably a default and a per-folder policies
* support for a concept of "archived offline" media i.e. media that has been backed up to the server, marked as backed up on a server and removed from the server would be treated as present on a server for the purposes of skipping backup of a non-modified media on a mobile device without it needing to be present on a server. Should the media be updated on a mobile, the normal update policies would apply
I've been using Resilio Sync on my Android device and my NAS. I bought a family license a couple years ago.
I haven't seen any apps that naively support gps or time based hooks, fwiw, but sync-vs-backup mode is a common feature.