Keep track of audio/video play position across devices

Describe the solution you’d like

If I’m halfway through listening to a long sermon with the new play widget, I’d like to be able to pick up any other device and continue listening there. I realize this may require the file to be downloaded to the new device, so in this case could you cache it forever on each device that “requests” it (by interacting with the play widget in any way)? If not forever, let me know how long it could be considered “interested” (in the IPFS sense).

Describe alternatives you’ve considered

Dropbox? Seriously I have no idea where the alternatives are.

Additional context

I might even like to auto-sync some or all of the audio files I upload, but I don’t want to chew up my phone’s storage, so I’d like to limit it somehow.