I'm trying to avoid having to parse the entirety of the api feedback when I just need a really simple boolean check on the other end.
Also, is query possible when send feedback is unchecked?
No direct message to do so, but you can send the message /layer/size/? to get a feedback stating the size of the media currently playing on the layer : if it is zero, it means that no media is playing.
And yes, "send feedback" has to be active.