The audio search functionality has been out a little while now, but I'm not yet aware of any ECP update to pass the audio to the Roku. What is the expected format for sending audio commands? Also, what is the compression type used for the audio stream?
Does not having public APIs also mean "don't do this because we'll get angry" or does it just mean "we don't have time to help with this." In principle, it seems one could sniff it. Or does it mean "we will publish this at some point soon so don't waste a few days trying to decode it."
It means, we don't have any published documentation for accessing the microphone button via ECP. The problem with implementing something for an undocumented API is that if the API changes it would break your app. I wouldn't hold your breath for anything like this being published in the immediate future. I don't think we have a problem with you experimenting, but if you want to publish a Roku Channel that does this, I can't say one way or the other if we would publish it, would have to see what it does and what the content team thinks about it.