Here is a demo of WebTorrent…
Here is a demo of WebTorrent hosting a 45 min video with only 1 seeder (currently me).
This page takes in the magnet link text and uses the browser as a torrent application to stream in the video.
At the moment it takes about 10 seconds to load initialy but with more seeders this gets exponentially faster. Also, every browser watching is also a seeder.