Something in a similar vein: BTFS, mount a torrent file (or magnet link) as a read only drive https://github.com/johang/btfs
It's really good, and use it a lot of times. Doesn't seem to be an active project anymore though but it still works
Some systems are more appropriate than just those options, but it requires player cooperation.
For instance on Android, NOVA Video Player supports torrent streaming. Or btplay from https://github.com/johang/btfs .
The way they work is better for the network, because it asks only for the N next MB from current position to be available ASAP, but the rest can be downloaded randomly to help the network like a standard client would do.
If you have the torrent file, you can use one of the things that mount them as virtual file systems, like btfs (https://github.com/johang/btfs).