Have you heard of [syncthing](https://syncthing.net/) ? It syncs a folder between devices, like Dropbox, without the need for someone else's computer. No cloud, it's just your pc talking to your phone, directly and automatically, through your home WiFi.
You can set connections between folders to be one-directional. That way after I send stuff to my intended device I wipe it from the source device and it stays where it was intended to go.