I have found some software that backs up your mobile phone once you enter into your home WIFI range. Just goes to prove that nothing is new. I thought I was going to have to write some code to do this.
Using Syncthing on the Raspberry Pi and Syncthing-fork on the Android phones.
Setting it up was very simple, the main configuration is via a web page. Simply add the path to where you want the files stored, set an advanced option to not to copy deletions and then add your mobile phone. I have set it to copy any new photos and videos from the camera/DCMI folder on the phone over to the NAS. They can then be shown on the TV, See Jukebox server.
I am going to run this just on my phone for week to see how it gets on and then roll it out to all the other phones in my network.