Re: Audio cast dongle - yes please
Well, more or less; but the casting system tends to involve your device not streaming directly to the receiver, but simply sending commands that say "play this stream, from this URL"
That means there are fewer hops, and even if the battery on the phone, for instance goes flat, the casting device carries on playing
In theory, you can do more smart things - I don't see why a few devices on the same home network couldn't sync playback between themselves, for instance. So, potentially it can offer a lot more flexibility than simply sending an audio stream over bluetooth.