Quite a bit of work overall I'd think as Gizmo has already said.
Not that it couldn't be done, but since you're the first person I recall asking for it it would probably take a LOT more interest in order to look at coding it into the product.
Again, though maybe good for some sites, as pointed out very few "shared" hosting solutions would support or allow such bandwidth usage. Even if they don't stop or prevent it, the speed would probably be too slow due to shared resources being too low. Streaming video in most cases would require a dedicated server or some very gracious shared hosting site.
